message: Add missing sub-headings to contents
diff: - [Records](#records)
  - [Field lookups](#field-lookups)
  - [Functions](#functions)
  + - [Simply typed functions](#simply-typed-functions)
  + - [Polymorphic functions](#polymorphic-functions)
  + - [Syntactic sugar for functions](#syntactic-sugar-for-functions)
  ## Declarations
  @@ -212,7 +215,7 @@ Pikelet> (\(x : Type) (x : a) => x) I32 1
  1 : I32
  ```
  -### Syntactic Sugar for functions
  +### Syntactic sugar for functions
  In Pikelet all functions take a single argument - in order to pass multiple
  arguments we use currying. The following functions are equivalent:
  