docs: include TOOD comment

lib/game/components/flipper.dart

@@ -142,6 +142,9 @@ class Flipper extends BodyComponent with KeyboardHandler {
     RawKeyEvent event,
     Set<LogicalKeyboardKey> keysPressed,
   ) {
+    // TODO(alestiago): Check why false cancels the event for other components.
+    // Investigate why return is of type [bool] expected instead of a type
+    // [KeyEventResult].
     if (!_keys.contains(event.logicalKey)) return true;
 
     if (event is RawKeyDownEvent) {