feat(ads): add interstitial ad trigger on topic item tap

- Import InterstitialAdManager and Bloc dependencies
- Add interstitial ad trigger logic in TopicItemWidget's onTap event

Author: fulleni

lib/headlines-search/widgets/topic_item_widget.dart

@@ -1,5 +1,7 @@
 import 'package:core/core.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_news_app_mobile_client_full_source_code/ads/interstitial_ad_manager.dart';
 import 'package:flutter_news_app_mobile_client_full_source_code/router/routes.dart';
 import 'package:go_router/go_router.dart';
 
@@ -21,6 +23,9 @@ class TopicItemWidget extends StatelessWidget {
             )
           : null,
       onTap: () {
+        context
+            .read<InterstitialAdManager>()
+            .onPotentialAdTrigger(context: context);
         context.pushNamed(
           Routes.entityDetailsName,
           pathParameters: {'type': ContentType.topic.name, 'id': topic.id},