Add Doc Comments to Allow Docs Generation

[ryanford]

Is your feature request related to a problem? Please describe.

Project could benefit from more thorough documentation. Demo examples are nice, but I think it could be better to show exactly what classes/API functions are available and how they are to be called, what the expected parameters are.

Describe the solution you'd like

Add LDoc or similar doc comments to generate docs.

Describe alternatives you've considered

Other alternative would be LuaDoc. These two are the most popular on LuaRocks.

Additional context

Generated docs would be comparable to Penlight's, T-Engine or similar.

[waruqi]

Looks good, I will consider improving the document later. Thanks!

[david-von-tamar]

Documentation is desperately needed.