Add Appendix A: Keywords to Sway book

docs/book/src/SUMMARY.md

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     - [forc explore](./forc/plugins/forc_explore.md)
     - [forc fmt](./forc/plugins/forc_fmt.md)
     - [forc lsp](./forc/plugins/forc_lsp.md)
+- [Appendix](./appendix/index.md)
+  - [Keywords](./appendix/keywords.md)

docs/book/src/appendix/index.md

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+# Appendix
+
+The following sections contain reference material you may find useful in your Sway journey.
+
+- [Keywords](./keywords.md)

docs/book/src/appendix/keywords.md

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+# [Appendix A: Keywords](#appendix-a-keywords)
+
+The following list contains keywords that are reserved for current or
+future use by the Sway language. As such, they cannot be used as
+identifiers. Identifiers are names of functions, variables,
+parameters, modules, constants, attributes, types or
+traits, ect.
+
+## [Keywords Currently in Use](#keywords-currently-in-use)
+
+The following is a list of keywords currently in use, with their
+functionality described.
+
+- `as` - rename items in `use` statements, eg `use type::a as alias_name`
+- [`abi`](https://fuellabs.github.io/sway/master/book/sway-program-types/smart_contracts.html#the-abi-declaration) - defines a smart contract ABI in a syntactcally similar way to traits
+- [`break`](https://fuellabs.github.io/sway/v0.44.0/book/basics/control_flow.html#break-and-continue) - exit a loop immediately
+- [`const`](https://fuellabs.github.io/sway/v0.44.0/book/basics/constants.html) - define constant items
+- [`continue`](https://fuellabs.github.io/sway/v0.44.0/book/basics/control_flow.html#break-and-continue) - continue to the next loop iteration
+- `else` - used in conjunction with `if` conditions for control flow constructs
+- [`enum`](https://fuellabs.github.io/sway/v0.44.0/book/basics/structs_tuples_and_enums.html#enums) - define an enumeration
+- `false` - Boolean false literal
+- [`fn`](https://fuellabs.github.io/sway/master/book/basics/functions.html)- define a function or the function pointer type
+- [`if`](https://fuellabs.github.io/sway/v0.44.0/book/basics/control_flow.html#if-expressions) - branch based on the result of a conditional expression
+- `impl` - implement inherent or trait functionality
+- `let` - bind a variable
+- [`match`](https://fuellabs.github.io/sway/v0.44.0/book/basics/control_flow.html#match-expressions) - exhaustfully match a value to patterns
+- `mod` - define a module
+- `mut` - denote mutability in references, or pattern bindings
+- `pub` - denote public visibility of Sway data structures, traits, or modules
+- `ref` - bind by reference
+- `return` - return early from a function
+- `Self` - a type alias for the type we are defining or implementing
+- `self` - method subject
+- [`struct`](https://fuellabs.github.io/sway/v0.44.0/book/basics/structs_tuples_and_enums.html#structs) - define a structure
+- [`trait`](https://fuellabs.github.io/sway/master/book/advanced/traits.html#declaring-a-trait) - define a trait
+- `true` - Boolean true literal
+- [`type`](https://fuellabs.github.io/sway/master/book/advanced/advanced_types.html?search=#creating-type-synonyms-with-type-aliases) - define a type alias or associated type
+- `use` - bring symbols into scope
+- `where` - specifies traits for generic types
+- [`while`](https://fuellabs.github.io/sway/v0.44.0/book/basics/control_flow.html#while) - loop conditionally based on the result of an expression
+
+## [Keywords Reserved for Possible Future Use](#keywords-reserved-for-possible-future-use)
+
+- `abstract`
+- `async`
+- `await`
+- `become`
+- `box`
+- `do`
+- `dyn`
+- `extern`
+- `for`
+- `in`
+- `loop`
+- `macro`
+- `move`
+- `override`
+- `priv`
+- `static`
+- `super`
+- `try`
+- `typeof`
+- `unsafe`
+- `unsized`
+- `virtual`
+- `yield`
+
+## [Special Keywords](#special-keywords)
+
+### [Program Keywords](#program-keywords)
+
+Keywords associated with defining the type of Sway program to compile
+
+- [`contract`](https://fuellabs.github.io/sway/master/book/sway-program-types/smart_contracts.html) - analogous to a deployed API with some database state
+- [`library`](https://fuellabs.github.io/sway/master/book/sway-program-types/libraries.html) - Sway code that defines new common behavior
+- [`predicate`](https://fuellabs.github.io/sway/master/book/sway-program-types/predicates.html) - programs that return a Boolean value and which represent ownership of some resource upon execution to true
+- [`script`](https://fuellabs.github.io/sway/master/book/sway-program-types/scripts.html) - a runnable bytecode on the chain, which executes once to preform a task
+
+### [Attribute Keywords](#attribute-keywords)
+
+Keywords associated with defining the funcitonallity of attributes
+
+- [`allow`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#allow) - overrides checks that would otherwise result in errors or warnings
+- [`doc`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#doc) - specifies documentation
+- [`inline`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#inline) - suggests that a copy of the attributed function should be placed in the caller, rather than generating code to call the function where it is defined
+- [`payable`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#payable) - implies method is payable for compile time
+- [`storage`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#storage) - declaration that contains a list of stored variables
+- [`test`](https://fuellabs.github.io/sway/master/book/reference/attributes.html#test) - marks a function to be executed as a test