Add LuaCATS doc standard for Lua

[shyun3]

Documentation standard

https://luals.github.io/wiki/annotations/

How popular is the doc standard?

• Not popular at all
• Some people use it
• Quite a lot of people use it
• It's not the most popular one, but a good alternative
• Everyone is using it

LuaCATS is the system of annotations used by the Lua Language Server. This system is not compatible with LDoc, which is currently the only Lua doc standard supported by doge (ldoc#403 might be relevant).