TF-3996 Add dividers for items in context menu on desktop

lib/features/base/extensions/popup_menu_action_list_extension.dart

@@ -0,0 +1,8 @@
+import 'package:core/presentation/extensions/iterable_extension.dart';
+import 'package:tmail_ui_user/features/base/model/popup_menu_item_action.dart';
+
+extension PopupMenuActionListExtension on List<PopupMenuItemAction> {
+  Map<int, List<PopupMenuItemAction>> groupByCategory() {
+    return groupBy<int>((action) => action.category, sortKeys: true);
+  }
+}