Update web files and add semantics

Signed-off-by: Nikolai Rodionov <iam@allanger.xyz>

lib/main.dart

@@ -5,6 +5,7 @@ import 'package:web/web.dart' as web;
 import 'package:flutter_dotenv/flutter_dotenv.dart';
 import 'package:flutter/material.dart';
 import 'package:grpc/grpc_web.dart';
+import 'package:flutter/semantics.dart';
 
 void main() async {
   await dotenv.load(fileName: ".env");
@@ -14,6 +15,7 @@ void main() async {
   );
 
   runApp(MyApp(channel: grpcChannel));
+  SemanticsBinding.instance.ensureSemantics();
 }
 
 class MyApp extends StatelessWidget {