CI: strict mypy check in github actions

mypy_files.txt is a list of files that will fail the CI if mypy finds errors in them

worlds/LauncherComponents.py

@@ -64,7 +64,7 @@ class SuffixIdentifier:
     def __init__(self, *args: str):
         self.suffixes = args
 
-    def __call__(self, path: str):
+    def __call__(self, path: str) -> bool:
         if isinstance(path, str):
             for suffix in self.suffixes:
                 if path.endswith(suffix):