feat(l10n): add localization extension for AppUserRole

- Create new extension on AppUserRole to provide localized string representations
- Add l10n method that returns localized name based on user role
- Include cases for guestUser, standardUser, and premiumUser
- Update imports to include necessary packages and localization files

Author: fulleni

lib/shared/extensions/app_user_role_l10n.dart

@@ -0,0 +1,21 @@
+import 'package:core/core.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
+
+/// {@template app_user_role_l10n}
+/// Extension on [AppUserRole] to provide localized string representations.
+/// {@endtemplate}
+extension AppUserRoleL10n on AppUserRole {
+  /// Returns the localized name for an [AppUserRole].
+  String l10n(BuildContext context) {
+    final l10n = context.l10n;
+    switch (this) {
+      case AppUserRole.guestUser:
+        return l10n.guestUserTab;
+      case AppUserRole.standardUser:
+        return l10n.authenticatedUserTab; // Using authenticatedUserTab for standardUser
+      case AppUserRole.premiumUser:
+        return l10n.premiumUserTab;
+    }
+  }
+}