feat(l10n): add extension for localized AdType descriptions

- Create AdTypeL10n extension on AdType enum
- Implement l10n method to return localized strings for each AdType
- Add import for context.l10n extension

Author: fulleni

lib/shared/extensions/ad_type_l10n.dart

@@ -0,0 +1,21 @@
+import 'package:core/core.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_news_app_web_dashboard_full_source_code/l10n/l10n.dart';
+
+/// Extension on [AdType] to provide localized descriptions.
+extension AdTypeL10n on AdType {
+  /// Returns a localized string for the [AdType] enum value.
+  String l10n(BuildContext context) {
+    final l10n = context.l10n;
+    switch (this) {
+      case AdType.banner:
+        return l10n.bannerAdType;
+      case AdType.native:
+        return l10n.nativeAdType;
+      case AdType.interstitial:
+        return l10n.interstitialAdType;
+      case AdType.video:
+        return l10n.videoAdType;
+    }
+  }
+}