🎨 Various changes

- Changed source additional data to dict
- Moved local cover saving into a manager
- Added stub for itch cover manager

src/importer/importer.py

@@ -120,7 +120,7 @@ class Importer:
             # Handle the result depending on its type
             if isinstance(iteration_result, Game):
                 game = iteration_result
-                additional_data = tuple()
+                additional_data = {}
             elif isinstance(iteration_result, tuple):
                 game, additional_data = iteration_result
             elif iteration_result is None: