Updated docs/haskell.md and docs/purescript.md to reflect the updated frontend tools

[jaredponn]

A short PR to update the documentation to use the tools in #121. This also:

• Changed the example to use lambda buffers prelude and hence use the opaque Char type (it won't compile otherwise without it)

[bladyjoker]

You're right, let's use Prelude for this:

That would change the schema for Document a bit...

module Document

-- We need the opaque Char type
import Prelude (Text, List, Set, Bytes)

-- Author
sum Author = Ivan | Jovan | Savo

-- Reviewer
sum Reviewer = Bob | Alice

-- Document
record Document a = {
  author : Author,
  reviewers : Set Reviewer,
  content : Chapter a
 }

-- Chapter
record Chapter a = {
  content : a,
  subChapters : List (Chapter a)
 }

-- Some actual content
sum RichContent = Image Bytes | Gif Bytes | Text Text

-- Rich document
prod RichDocument = (Document RichContent)

[bladyjoker]

Thank you!

[jaredponn]

Thank you for the feedback! I'll rebase and merge this now.