新增断开wifi连接方法

lib/plugin/wifi_plugin.dart

@@ -15,4 +15,9 @@ class WiFiPlugin {
     static Future<void> connect(String ssid,String bssid,String password) async {
       return await _channel.invokeMethod("connect",{"ssid":ssid,"bssid":bssid,"password":password});
     }
+
+    // 断开wifi
+    static Future<void> disconnect() async {
+        return await _channel.invokeMethod("disconnect");
+    }
 }