[Docs] Separate pages for environments

[badosu]

Recoil has many different environment on which games can be programmed in Lua:

• LuaIntro (For loading screens before games)
• LuaMenu (For lobbies built in lua)
• LuaUI (Unsynced)
• Unsynced LuaRules (Shares most of API with LuaUI)
• Synced LuaRules

We want to be able to offer a way for gamedevs to find what APIs are available on which environment they're coding for. Spring Wiki (which was manually curated) and the previous LDoc (which was per file) did not fulfill all these but they had segmented pages for Unsynced and Synced environments (which is the brunt of gamedev experience).

Ideally we'd have all these covered, but just Synced/Unsynced would be a big step forwards from current.