I believe the repeated code can be generated with procedural macros, but
I don't need that right now. I'll do it if I ever end up needing this.
Right now I need to start making the game itself more than anything.
- Implements a new macro to generate code for a new structure: TypeMap
- TypeMaps are wrappers for HashMaps that use TypeIDs as keys.
- Refactor the entire codebase to use the new resource structures.
- This commit is the first step towards getting rid of "god context objects everywhere".
