feat: made Mocks be Mocks

packages/pinball_flame/test/helpers/mocks.dart

@@ -1,8 +1,10 @@
 import 'package:flame/components.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:mocktail/mocktail.dart';
 
-class MockForge2DGame extends Forge2DGame {}
+class MockForge2DGame extends Mock implements Forge2DGame {}
 
-class MockContactCallback extends ContactCallback<dynamic, dynamic> {}
+class MockContactCallback extends Mock
+    implements ContactCallback<dynamic, dynamic> {}
 
-class MockComponent extends Component {}
+class MockComponent extends Mock implements Component {}