chore: Don't publish .ts or testing files

Before this change, we publish .ts source files to the same directory as the .js/.d.ts files to npm.

That means when a consumer imports a @material/web module with TypeScript, TypeScript prefers the .ts file over the .d.ts file when to load that module's types.

That in turn means the consumer's TypeScript type-checks the entire @material/web .ts file, including its private implementation details (private fields, etc.). If the consumer's tsconfig.json is configured more strictly than @material/web's was (e.g. if noUnusedParameters is true), or if some additional ambient types are loaded (e.g. @types/node is installed, which changes the signature of setTimeout), they would get a compile error.

This change stops publishing .ts files to npm to solve that problem for consumers.

This also includes some related changes:

- Sets inlineSources to true. This puts the .ts file contents directly inside the .js.map file, instead of linking to the .ts path. Otherwise sourcemaps would not work.

- Sets declarationMap to false. This removes the .d.ts.map files, which are not useful without the .ts paths, because there is no equivalent to inlineSources for declarationMap (see microsoft/TypeScript#38966).

- Replaces .npmignore blocklist with package.json files allowlist (which I find to be a bit safer), and adds new omissions for testing files, which don't need to be published.

Note that this doesn't solve the problem when using "npm link" for local cross-package development, because in that case the .ts files will still be present. So a better solution to this problem would be to have a separate src/ directory for .ts source files. That will require a Copybara transform to move the files. We can discuss this separately and do it as a followup if agreed.

PiperOrigin-RevId: 469833263

package.json

@@ -21,6 +21,16 @@
     "prebuild:ts": "find . -name '*.css' -type f | xargs node css-to-ts.js",
     "build:ts": "tsc"
   },
+  "files": [
+    "**/*.js",
+    "**/*.js.map",
+    "**/*.d.ts",
+    "**/*.scss",
+    "!css-to-ts.js",
+    "!**/test/**",
+    "!**/testing/**",
+    "!**/*_test.*"
+  ],
   "dependencies": {
     "lit": "^2.3.0",
     "tslib": "^2.4.0"

tsconfig.json

@@ -3,7 +3,7 @@
     "allowUnreachableCode": false,
     "baseUrl": ".",
     "declaration": true,
-    "declarationMap": true,
+    "declarationMap": false,
     "downlevelIteration": true,
     "emitDecoratorMetadata": true,
     "experimentalDecorators": true,
@@ -22,6 +22,7 @@
     },
     "skipLibCheck": true,
     "sourceMap": true,
+    "inlineSources": true,
     "strict": true,
     "strictNullChecks": false,
     "target": "es2020"