feat: add OnDestroy method to clear view stack

Author: BlenMiner

Assets/PurrUI/Runtime/ViewStack.cs

@@ -547,5 +547,10 @@ private static IEnumerator RunExitTransition(MonoView view, IEnumerator transiti
             yield return transition;
             if (view) view.DestroyMe();
         }
+
+        private void OnDestroy()
+        {
+            Clear();
+        }
     }
 }