Add background images for games

lib/db.dart

@@ -17,7 +17,8 @@ CREATE TABLE IF NOT EXISTS games (
   last_played TEXT NOT NULL,
   rss_feed_url TEXT NOT NULL,
   version_regex TEXT NOT NULL,
-  last_updated TEXT NOT NULL
+  last_updated TEXT NOT NULL,
+  image_data BLOB
 );
 CREATE INDEX IF NOT EXISTS idx_games_name ON games (name);
 CREATE UNIQUE INDEX IF NOT EXISTS idx_games_name_unique ON games (name);