fix UIWIdgets pass events to children in wrong order (#2553)

Author: eruvanos

arcade/gui/widgets/__init__.py

@@ -186,7 +186,7 @@ def on_event(self, event: UIEvent) -> Optional[bool]:
 
         if self.visible:
             # pass event to children
-            for child in self.children:
+            for child in reversed(self.children):
                 if child.dispatch_event("on_event", event):
                     return EVENT_HANDLED