Markdown generator: Convert ocamldoc markup to markdown

[gaborigloi]

See #100 (comment)

[gaborigloi]

@mseri found this helpful project - it may be easier than we expected to parse the ocamldoc syntax:
https://github.com/ocaml-doc/octavius
We can use it like this: https://github.com/ocaml-doc/doc-ock-html
This might also help: https://github.com/ocaml/omd