update extension sample

新增示例代码HandleBaseExtension

Assets/YooAsset/Samples~/Extension Sample/Runtime/ExtensionClass/HandleBaseExtension.cs

@@ -0,0 +1,12 @@
+using System.Collections;
+using System.Collections.Generic;
+using UnityEngine;
+using YooAsset;
+
+public static class HandleBaseExtension
+{
+    public static bool IsSucceed(this HandleBase thisHandle)
+    {
+        return thisHandle.IsDone && thisHandle.Status == EOperationStatus.Succeed;
+    }
+}