message: Document booleans
diff: Pikelet has a number of builtin types, which we now describe here:
  +## Booleans
  +
  +```pikelet
  +Bool : Type
  +```
  +
  +Booleans have two constructors, `true` and `false`:
  +
  +```pikelet
  +true : Type
  +false : Type
  +```
  +
  ## Unsigned integers
  Unsigned integers are defined via the following built-ins:
  @@ -41,7 +54,7 @@ Signed integers can be constructed using numeric literals:
  0x2F : S16
  ```
  -## Floating point
  +## Floating point numbers
  ```pikelet
  F32 : Type
  