Add proxy routing and sing-box support

packages/flutter_singbox_proxy/example/integration_test/plugin_integration_test.dart

@@ -0,0 +1,23 @@
+// This is a basic Flutter integration test.
+//
+// Since integration tests run in a full Flutter application, they can interact
+// with the host side of a plugin implementation, unlike Dart unit tests.
+//
+// For more information about Flutter integration tests, please see
+// https://flutter.dev/to/integration-testing
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:integration_test/integration_test.dart';
+
+import 'package:flutter_singbox_proxy/flutter_singbox_proxy.dart';
+
+void main() {
+  IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+
+  testWidgets('getState test', (WidgetTester tester) async {
+    final FlutterSingboxProxy plugin = FlutterSingboxProxy();
+    final state = await plugin.getState();
+
+    expect(state.status, SingboxProxyRuntimeStatus.stopped);
+  });
+}