增加壳子接口

lib/services/platform.dart

@@ -701,6 +701,12 @@ class PlatformService extends JsonRpcClientBase {
     var rpcRst = await call('SetSystemAudioDevice', [deviceName]);
     return rpcRst;
   }
+
+  ///停止魔盒的设备预览
+  Future<bool> stopPreview() async {
+    var rpcRst = await call('StopPreview');
+    return rpcRst;
+  }
 }
 
 /// 一些platform 的数据结构定义