Codegen an entrypoint for flutter web applications (#33956)

packages/flutter_tools/lib/src/project.dart

diff --git a/packages/flutter_tools/lib/src/project.dart b/packages/flutter_tools/lib/src/project.dart
index 6b51446..03efe52 100644
--- a/packages/flutter_tools/lib/src/project.dart
+++ b/packages/flutter_tools/lib/src/project.dart
@@ -583,6 +583,9 @@
     return parent.directory.childDirectory('web').existsSync();
   }
 
+  /// The html file used to host the flutter web application.
+  File get indexFile => parent.directory.childDirectory('web').childFile('index.html');
+
   Future<void> ensureReadyForPlatformSpecificTooling() async {
     /// Generate index.html in build/web. Eventually we could support
     /// a custom html under the web sub directory.