Add proxy routing and sing-box support

packages/flutter_singbox_proxy/example/lib/main.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_singbox_proxy/flutter_singbox_proxy.dart';
+
+void main() {
+  runApp(const MyApp());
+}
+
+class MyApp extends StatelessWidget {
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final proxy = FlutterSingboxProxy();
+    return MaterialApp(
+      home: Scaffold(
+        appBar: AppBar(title: const Text('Plugin example app')),
+        body: FutureBuilder<SingboxProxyRuntimeState>(
+          future: proxy.getState(),
+          builder: (context, snapshot) {
+            final status = snapshot.data?.status.name ?? 'unknown';
+            return Center(child: Text('sing-box proxy status: $status'));
+          },
+        ),
+      ),
+    );
+  }
+}