When the UI consumes an input, don't send it to the game

src/window.rs

@@ -28,10 +28,12 @@ pub trait AppWindow {
         let _ = render_state;
     }
     fn on_destroy(&mut self) {}
-    fn handle_key_event(&mut self, event: &KeyEvent) {
+    fn handle_key_event(&mut self, event: &KeyEvent) -> bool {
         let _ = event;
+        false
     }
-    fn handle_gamepad_event(&mut self, event: &gilrs::Event) {
+    fn handle_gamepad_event(&mut self, event: &gilrs::Event) -> bool {
         let _ = event;
+        false
     }
 }