I recently spent a bit of time designing a VLC extension and wrote some simple documentation to help me more easily keep track of which Lua modules did what. I've worked on it a bit since then, added some markdown styling and uploaded it to my Github site.
Here are the modules I've documented: https://verghost.com/vlc-lua-docs/m/
Also, here's the Github repo: https://github.com/verghost/vlc-lua-docs