Request for ability to skip adding to documentation, i.e. `---@nodoc`

[wauterboi]

At the moment, if I do anything that references _G, all of the documentation for _G populates the documentation. It would be nice to be able to prevent superfluous documentation - especially for stuff that's only local to the file and not exported for public use.

[sumneko]

The markdown file is for demonstration only. The document should be generated by yourself from the JSON file. Filter out unnecessary documents according to your own rules during the generation process.