TEngine全面更新，升级YooAsset2.1.1、UniTask、UIWindow、I2Localization

TEngine全面更新，升级YooAsset2.1.1、UniTask、UIWindow、I2Localization

UnityProject/Packages/YooAsset/Runtime/DownloadSystem/DownloadHelper.cs

@@ -0,0 +1,41 @@
+using System;
+using System.IO;
+using System.Collections;
+using System.Collections.Generic;
+using System.Threading;
+using UnityEngine.Networking;
+
+namespace YooAsset
+{
+    /// <summary>
+    /// 自定义下载器的请求委托
+    /// </summary>
+    public delegate UnityWebRequest DownloadRequestDelegate(string url);
+
+
+    internal static class DownloadHelper
+    {
+        /// <summary>
+        /// 下载失败后清理文件的HTTP错误码
+        /// </summary>
+        public static List<long> ClearFileResponseCodes { set; get; }
+
+        /// <summary>
+        /// 自定义下载器的请求委托
+        /// </summary>
+        public static DownloadRequestDelegate RequestDelegate = null;
+
+        /// <summary>
+        /// 创建一个新的网络请求
+        /// </summary>
+        public static UnityWebRequest NewRequest(string requestURL)
+        {
+            UnityWebRequest webRequest;
+            if (RequestDelegate != null)
+                webRequest = RequestDelegate.Invoke(requestURL);
+            else
+                webRequest = new UnityWebRequest(requestURL, UnityWebRequest.kHttpVerbGET);
+            return webRequest;
+        }
+    }
+}