Use document comments for stdlib and create documentation during deploy

[stefandeml]

Currently we document stdlib functions in two places: in the .code file and in the mdbook docs.

Document comments would make it easy to document as you write code. This also makes it easier to keep your documentation up to date as you’re modifying code.

I would suggest document comments are denoted by a /// and support Markdown.

[stefandeml]

I wrote a simple Python script now to use it myself for this issue: https://github.com/Zokrates/ZoKrates/issues/244

Could be added to the build / deploy pipeline at a later point in time