message: Add a list of keywords to the docs
diff: - [Primitive types and their literals](#primitive-types-and-their-literals)
  - [Type annotations](#type-annotations)
  - [Identifiers](#identifiers)
  +- [Keywords](#keywords)
  ## Comments
  @@ -64,3 +65,27 @@ error: found a floating point literal, but expected a type `U64`
  ## Identifiers
  > TODO
  +
  +## Keywords
  +| Keyword | Documentation |
  +|----------|-------------------------------------------|
  +| `as` | [internal field names] |
  +| `case` | [case expressions] |
  +| `else` | [if-then-else-expressions] |
  +| `extern` | |
  +| `if` | [if-then-else-expressions] |
  +| `import` | |
  +| `in` | [bindings] |
  +| `let` | [bindings] |
  +| `record` | [record] values |
  +| `Record` | [Record] types |
  +| `Type` | [polymorphic functions], [types of types] |
  +| `where` | |
  +
  +[if-then-else-expressions]: conditionals.html#if-then-else-expressions
  +[case expressions]: conditionals.html#case-expressions
  +[bindings]: bindings.html
  +[record]: records.html
  +[polymorphic functions]: functions.html
  +[types of types]: universes.html#types-of-types
  +[internal field names]: records.html#external-vs-internal-field-names
  