[New]引力引擎插件新增AppId参数

plugin/gravity_engine/lib/gravity_engine.dart

@@ -4,10 +4,10 @@ import 'gravity_engine_platform_interface.dart';
 class GravityEngine {
   GravityEngine._();
 
-  static Future<bool> initialize(
-      String accessToken, String clientId, String channel, bool debug) {
+  static Future<bool> initialize(String appId, String accessToken,
+      String clientId, String channel, bool debug) {
     return GravityEnginePlatform.instance
-        .initialize(accessToken, clientId, channel, debug);
+        .initialize(appId, accessToken, clientId, channel, debug);
   }
 
   static Future<void> trackEvent(

plugin/gravity_engine/lib/gravity_engine_method_channel.dart

@@ -12,11 +12,12 @@ class MethodChannelGravityEngine extends GravityEnginePlatform {
   /// Initializes the Gravity Engine SDK.
   /// Returns `true` if the user is attributed, `false` otherwise.
   @override
-  Future<bool> initialize(
-      String accessToken, String clientId, String channel, bool debug) async {
+  Future<bool> initialize(String appId, String accessToken, String clientId,
+      String channel, bool debug) async {
     final result = await methodChannel.invokeMethod<bool>(
       'initialize',
       <String, dynamic>{
+        'appId': appId,
         'accessToken': accessToken,
         'debug': debug,
         'clientId': clientId,

plugin/gravity_engine/lib/gravity_engine_platform_interface.dart

@@ -23,8 +23,8 @@ abstract class GravityEnginePlatform extends PlatformInterface {
     _instance = instance;
   }
 
-  Future<bool> initialize(
-      String accessToken, String clientId, String channel, bool debug) {
+  Future<bool> initialize(String appId, String accessToken, String clientId,
+      String channel, bool debug) {
     throw UnimplementedError('initialize() has not been implemented.');
   }