add fall-through for InputAction.ZOOM for Third Person camera delegate

thermion_dart/lib/src/input/src/implementations/third_person_camera_delegate.dart

@@ -56,6 +56,8 @@ class OverTheShoulderCameraDelegate implements InputHandlerDelegate {
         break;
       case InputAction.NONE:
         break;
+      case InputAction.ZOOM:
+        break;
     }
   }