fix: Set hitbox debugColor to yellow (#2958)

To easily be able to spot whether a it is a hitbox that is being drawn
in `debugMode = true` it is now yellow instead of purple like the other
debug boxes.

packages/flame/lib/src/collisions/hitboxes/shape_hitbox.dart

@@ -1,5 +1,6 @@
 import 'package:flame/collisions.dart';
 import 'package:flame/components.dart';
+import 'package:flame/extensions.dart';
 import 'package:flame/game.dart';
 import 'package:flame/geometry.dart';
 import 'package:flame/src/geometry/shape_intersections.dart'
@@ -20,6 +21,9 @@ mixin ShapeHitbox on ShapeComponent implements Hitbox<ShapeHitbox> {
     collisionTypeNotifier.value = type;
   }
 
+  @override
+  Color debugColor = const Color(0xFFFFFF00);
+
   @override
   CollisionType get collisionType => collisionTypeNotifier.value;