Implemented named constant

lib/core/constants.dart

@@ -28,4 +28,7 @@ class Constants {
 
   /// Duration in milliseconds for the fade-in animation of texts.
   static const int fadeInDuration = 300;
+
+  /// Duration in milliseconds for the keyboard to fully disappear.
+  static const int kKeyboardDelay = 300;
 }

lib/presentation/views/create_game_view.dart

@@ -298,7 +298,9 @@ class _CreateGameViewState extends State<CreateGameView> {
                     ),
                     onPressed: () {
                       FocusScope.of(context).unfocus();
-                      Future.delayed(const Duration(milliseconds: 300), () {
+                      Future.delayed(
+                          const Duration(
+                              milliseconds: Constants.kKeyboardDelay), () {
                         _checkAllGameAttributes();
                       });
                     },