修改美洽为present方式打开

ios/Classes/SwiftFlutterMeiqiaPlugin.swift

@@ -52,6 +52,8 @@ public class SwiftFlutterMeiqiaPlugin: NSObject, FlutterPlugin {
     func pushToMeiqiaVC(_ call: FlutterMethodCall,result: @escaping FlutterResult) {
         //跳转聊天界面
         let vc = MQChatViewManager.init()
+        let style = manager.chatViewStyle
+        style?.navBackButtonImage = UIImage.init(named: "back_black_icon")
         vc.pushMQChatViewController(in: navigationController())
         result(true);
     }