Attach DEACTIVATE/ACTIVATE events to stage.nativeWindow. (#3260)

* Update FlxGame.hx

* Fix for `flash` and `html5`.

* Fix compatibility with `openfl` `9.2.2`.

flixel/FlxGame.hx

@@ -358,6 +358,9 @@ class FlxGame extends Sprite
 		#if (desktop && openfl <= "4.0.0")
 		stage.addEventListener(FocusEvent.FOCUS_OUT, onFocusLost);
 		stage.addEventListener(FocusEvent.FOCUS_IN, onFocus);
+		#elseif (sys && openfl >= "9.3.0")
+		stage.nativeWindow.addEventListener(Event.DEACTIVATE, onFocusLost);
+		stage.nativeWindow.addEventListener(Event.ACTIVATE, onFocus);
 		#else
 		stage.addEventListener(Event.DEACTIVATE, onFocusLost);
 		stage.addEventListener(Event.ACTIVATE, onFocus);
@@ -918,4 +921,4 @@ private class FlxIntroSplash extends FlxSplash
 		FlxG.game._gameJustStarted = true;
 		super.startOutro(onOutroComplete);
 	}
-}
+}