🎨 Various changes

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

src/store/managers/itch_cover_manager.py

@@ -0,0 +1,19 @@
+from urllib3.exceptions import SSLError
+
+import requests
+from requests import HTTPError
+
+from src.game import Game
+from src.store.managers.async_manager import AsyncManager
+from src.store.managers.local_cover_manager import LocalCoverManager
+
+
+class ItchCoverManager(AsyncManager):
+    """Manager in charge of downloading the game's cover from itch.io"""
+
+    run_after = set((LocalCoverManager,))
+    retryable_on = set((HTTPError, SSLError))
+
+    def manager_logic(self, game: Game, additional_data: dict) -> None:
+        # TODO move itch cover logic here
+        pass