Provide API headers for sumneko's language server

[AFCMS]

https://github.com/LuaLS/lua-language-server

[GreenXenith]

I would like to see if it is feasible to write a script to generate most of the headers from the lua_api.txt; This is how snippets are currently generated, so I expect it should be possible. Post-cleanup would be acceptable.

[AFCMS]

We easily get a list of available functions, bot it won't annotate the parameters reliably.

Here is the headers that will result from the merge of @lua-rocks work and my work:

https://github.com/minetest-toolkit/minetest-lsp-api