Update descriptions for all compiler options

[orta]

Back at the end of 2020 we had a series of meetings going through all the tsconfig options, revising their descriptions and making them all consistent. They were then moved into the website, with the goal of bringing them upstream later. Today is that later, heh.

Overview of the new descriptions:

❯ node built/local/tsc.js --help --all
Version 4.4.0-dev
Syntax:   tsc [options] [file...]

Examples: tsc hello.ts
          tsc --outFile file.js file.ts
          tsc @args.txt
          tsc --build tsconfig.json

Options:
 --all                                              Show all compiler options.
 --allowJs                                          Allow JavaScript files to be a part of your program. Use the `checkJS` option to get errors from these files.
 --allowSyntheticDefaultImports                     Allow 'import x from y' when a module doesn't have a default export.
 --allowUmdGlobalAccess                             Allow accessing UMD globals from modules.
 --allowUnreachableCode                             Disable error reporting for unreachable code.
 --allowUnusedLabels                                Disable error reporting for unused labels.
 --alwaysStrict                                     Ensure 'use strict' is always emitted.
 --assumeChangesOnlyAffectDirectDependencies        Have recompiles in projects that use `incremental` and `watch` mode assume that changes within a file will only affect files directly depending on it.
 --baseUrl                                          Specify the base directory to resolve non-relative module names.
 -b, --build                                        Build one or more projects and their dependencies, if out of date
 --charset                                          No longer supported. In early versions, manually set the text encoding for reading files.
 --checkJs                                          Enable error reporting in type-checked JavaScript files.
 --composite                                        Enable constraints that allow a TypeScript project to be used with project references.
 -d, --declaration                                  Generate .d.ts files from TypeScript and JavaScript files in your project.
 --declarationDir DIRECTORY                         Specify the output directory for generated declaration files.
 --declarationMap                                   Create sourcemaps for d.ts files.
 --diagnostics                                      Output compiler performance information after building.
 --disableReferencedProjectLoad                     Reduce the number of projects loaded automatically by TypeScript.
 --disableSizeLimit                                 Remove the 20mb cap on total source code size for JavaScript files in the TypeScript language server.
 --disableSolutionSearching                         Opt a project out of multi-project reference checking when editing.
 --disableSourceOfProjectReferenceRedirect          Disable preferring source files instead of declaration files when referencing composite projects
 --downlevelIteration                               Emit more compliant, but verbose and less performant JavaScript for iteration.
 --emitBOM                                          Emit a UTF-8 Byte Order Mark (BOM) in the beginning of output files.
 --emitDeclarationOnly                              Only output d.ts files and not JavaScript files.
 --emitDecoratorMetadata                            Emit design-type metadata for decorated declarations in source files.
 --esModuleInterop                                  Emit additional JavaScript to ease support for importing CommonJS modules. This enables `allowSyntheticDefaultImports` for type compatibility.
 --experimentalDecorators                           Enable experimental support for TC39 stage 2 draft decorators.
 --explainFiles                                     Print files read during the compilation including why it was included.
 --extendedDiagnostics                              Output more detailed compiler performance information after building.
 --forceConsistentCasingInFileNames                 Ensure that casing is correct in imports.
 --generateCpuProfile FILE OR DIRECTORY             Emit a v8 CPU profile of the compiler run for debugging.
 --generateTrace DIRECTORY                          Generates an event trace and a list of types.
 -h, --help                                         Print this message.
 --importHelpers                                    Allow importing helper functions from tslib once per project, instead of including them per-file.
 --importsNotUsedAsValues                           Specify emit/checking behavior for imports that are only used for types
 -i, --incremental                                  Enable incremental compilation
 --init                                             Initializes a TypeScript project and creates a tsconfig.json file.
 --inlineSourceMap                                  Include sourcemap files inside the emitted JavaScript.
 --inlineSources                                    Include source code in the sourcemaps inside the emitted JavaScript.
 --isolatedModules                                  Ensure that each file can be safely transpiled without relying on other imports.
 --jsx KIND                                         Specify what JSX code is generated.
 --jsxFactory                                       Specify the JSX factory function used when targeting React JSX emit, e.g. 'React.createElement' or 'h'
 --jsxFragmentFactory                               Specify the JSX Fragment reference used for fragments when targeting React JSX emit e.g. 'React.Fragment' or 'Fragment'.
 --jsxImportSource                                  Specify module specifier used to import the JSX factory functions when using `jsx: react-jsx*`.`
 --keyofStringsOnly                                 Make keyof only return strings instead of string, numbers or symbols. Legacy option.
 --lib                                              Specify a set of bundled library declaration files that describe the target runtime environment.
                                                      'es5' 'es6' 'es2015' 'es7' 'es2016' 'es2017' 'es2018' 'es2019' 'es2020' 'es2021' 'esnext' 'dom' 'dom.iterable' 'webworker' 'webworker.importscripts' 'webworker.iterable' 'scripthost' 'es2015.core' 'es2015.collection' 'es2015.generator' 'es2015.iterable' 'es2015.promise' 'es2015.proxy' 'es2015.reflect' 'es2015.symbol' 'es2015.symbol.wellknown' 'es2016.array.include' 'es2017.object' 'es2017.sharedmemory' 'es2017.string' 'es2017.intl' 'es2017.typedarrays' 'es2018.asyncgenerator' 'es2018.asynciterable' 'es2018.intl' 'es2018.promise' 'es2018.regexp' 'es2019.array' 'es2019.object' 'es2019.string' 'es2019.symbol' 'es2020.bigint' 'es2020.promise' 'es2020.sharedmemory' 'es2020.string' 'es2020.symbol.wellknown' 'es2020.intl' 'es2021.promise' 'es2021.string' 'es2021.weakref' 'esnext.array' 'esnext.symbol' 'esnext.asynciterable' 'esnext.intl' 'esnext.bigint' 'esnext.string' 'esnext.promise' 'esnext.weakref' 
 --listEmittedFiles                                 Print the names of emitted files after a compilation.
 --listFiles                                        Print all of the files read during the compilation.
 --listFilesOnly                                    Print names of files that are part of the compilation and then stop processing.
 --locale                                           Set the language of the messaging from TypeScript. This does not affect emit.
 --mapRoot LOCATION                                 Specify the location where debugger should locate map files instead of generated locations.
 --maxNodeModuleJsDepth                             Specify the maximum folder depth used for checking JavaScript files from `node_modules`. Only applicable with `allowJs`.
 -m KIND, --module KIND                             Specify what module code is generated.
 --moduleResolution STRATEGY                        Specify how TypeScript looks up a file from a given module specifier.
 --newLine NEWLINE                                  Set the newline character for emitting files.
 --noEmit                                           Disable emitting file from a compilation.
 --noEmitHelpers                                    Disable generating custom helper functions like `__extends` in compiled output.
 --noEmitOnError                                    Disable emitting files if any type checking errors are reported.
 --noErrorTruncation                                Disable truncating types in error messages.
 --noFallthroughCasesInSwitch                       Enable error reporting for fallthrough cases in switch statements.
 --noImplicitAny                                    Enable error reporting for expressions and declarations with an implied `any` type..
 --noImplicitOverride                               Add `undefined` to a type when accessed using an index.
 --noImplicitReturns                                Enable error reporting for codepaths that do not explicitly return in a function.
 --noImplicitThis                                   Enable error reporting when `this` is given the type `any`.
 --noImplicitUseStrict                              Disable adding 'use strict' directives in emitted JavaScript files.
 --noLib                                            Disable including any library files, including the default lib.d.ts.
 --noPropertyAccessFromIndexSignature               Enforces using indexed accessors for keys declared using an indexed type
 --noResolve                                        Disallow `import`s, `require`s or `<reference>`s from expanding the number of files TypeScript should add to a project.
 --noStrictGenericChecks                            Disable strict checking of generic signatures in function types.
 --noUncheckedIndexedAccess                         Include 'undefined' in index signature results
 --noUnusedLocals                                   Enable error reporting when a local variables aren't read.
 --noUnusedParameters                               Raise an error when a function parameter isn't read
 --out FILE                                         Deprecated setting. Use `outFile` instead.
 --outDir DIRECTORY                                 Specify an output folder for all emitted files.
 --outFile FILE                                     Specify a file that bundles all outputs into one JavaScript file. If `declaration` is true, also designates a file that bundles all .d.ts output.
 --paths                                            Specify a set of entries that re-map imports to additional lookup locations.
 --plugins                                          List of language service plugins.
 --preserveConstEnums                               Disable erasing `const enum` declarations in generated code.
 --preserveSymlinks                                 Disable resolving symlinks to their realpath. This correlates to the same flag in node.
 --preserveWatchOutput                              Disable wiping the console in watch mode
 --pretty                                           Enable color and formatting in output to make compiler errors easier to read
 -p FILE OR DIRECTORY, --project FILE OR DIRECTORY  Compile the project given the path to its configuration file, or to a folder with a 'tsconfig.json'.
 --reactNamespace                                   Specify the object invoked for `createElement`. This only applies when targeting `react` JSX emit.
 --removeComments                                   Disable emitting comments.
 --resolveJsonModule                                Enable importing .json files
 --rootDir LOCATION                                 Specify the root folder within your source files.
 --rootDirs                                         Allow multiple folders to be treated as one when resolving modules.
 --showConfig                                       Print the final configuration instead of building.
 --skipDefaultLibCheck                              Skip type checking .d.ts files that are included with TypeScript.
 --skipLibCheck                                     Skip type checking all .d.ts files.
 --sourceMap                                        Create source map files for emitted JavaScript files.
 --sourceRoot LOCATION                              Specify the root path for debuggers to find the reference source code.
 --strict                                           Enable all strict type-checking options.
 --strictBindCallApply                              Check that the arguments for `bind`, `call`, and `apply` methods match the original function.
 --strictFunctionTypes                              When assigning functions, check to ensure parameters and the return values are subtype-compatible.
 --strictNullChecks                                 When type checking, take into account `null` and `undefined`.
 --strictOptionalProperties                         Enable strict checking of optional properties.
 --strictPropertyInitialization                     Check for class properties that are declared but not set in the constructor.
 --stripInternal                                    Disable emitting declarations that have `@internal` in their JSDoc comments.
 --suppressExcessPropertyErrors                     Disable reporting of excess property errors during the creation of object literals.
 --suppressImplicitAnyIndexErrors                   Suppress `noImplicitAny` errors when indexing objects that lack index signatures.
 -t VERSION, --target VERSION                       Set the JavaScript language version for emitted JavaScript and include compatible library declarations.
 --traceResolution                                  Log paths used during the `moduleResolution` process.
 --tsBuildInfoFile FILE                             Specify the folder for .tsbuildinfo incremental compilation files.
 --typeRoots                                        Specify multiple folders that act like `./node_modules/@types`.
 --types                                            Specify type package names to be included without being referenced in a source file.
 --useDefineForClassFields                          Emit ECMAScript-standard-compliant class fields.
 -v, --version                                      Print the compiler's version.
 -w, --watch                                        Watch input files.
 @<file>                                            Insert command line options and files from a file.

[orta]

Note: I haven't removed all the unused diags, I'm waiting on getting #44324 merged so that I can just do it in a single pass rather than have this collect merge conflicts with time

[orta]

Linking my script for grabbing a bunch of these from the site and syncing them: https://gist.github.com/orta/f8f94b4b52eba847d2cf016a1d281730