Add conditional override for webview_flutter_android

Introduced a conditional block in pubspec.yaml to override the webview_flutter_android dependency only if 'flet_webview' is present in the dependencies. This improves template flexibility for different dependency configurations.

{{cookiecutter.out_dir}}/pubspec.yaml

@@ -40,6 +40,10 @@ dependency_overrides:
   window_manager: ^0.4.3
   webview_flutter_android: 4.10.1
 
+# {% if 'flet_webview' in cookiecutter.flutter.dependencies %}
+  #webview_flutter_android: 4.10.1
+# {% endif %}
+
 # {% if 'flet_audio_recorder' in cookiecutter.flutter.dependencies %}
   record: ^5.1.1
 # {% endif %}