Make lua definition files for OSPGL API

[tatjam]

This will allow lua language servers (such as sumneko_lua) to understand the API of the game and offer autocompletion. This should be done once the API is a bit more established to avoid a lot of changes later on, but has to be done early so writing lua code is comfortable.

The definition files are basically a list of functions, objects and their documentation in lua format. They may be stored in another repo if needed, but it could be convenient to have them here too.

[tatjam]

Done, although any new additions to the game libraries need to be reflected on these files. Definitions can be found on res/.luadef/definitions/