Add license to example

pkgs/http_multi_server/example/main.dart

diff --git a/pkgs/http_multi_server/example/main.dart b/pkgs/http_multi_server/example/main.dart
index 661b52e..6e90c8b 100644
--- a/pkgs/http_multi_server/example/main.dart
+++ b/pkgs/http_multi_server/example/main.dart
@@ -1,3 +1,7 @@
+// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
 import 'package:http_multi_server/http_multi_server.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;