Replace contexts with resources

- 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".

Cargo.toml

@@ -6,5 +6,5 @@ members = [
     "asset",
     "game",
     "ecs",
-    "engine"
+    "engine",
 ]