docs: 更新示例项目

samples/SKIT.FlurlHttpClient.Wechat.TenpayV3.Sample_NetFramework48/Models/CreateRefundRequest.cs

@@ -0,0 +1,15 @@
+namespace SKIT.FlurlHttpClient.Wechat.TenpayV3.Sample.Models
+{
+    public class CreateRefundRequest
+    {
+        public string MerchantId { get; set; }
+
+        public string TransactionId { get; set; }
+
+        // NOTICE:
+        //   单机演示时金额来源于客户端请求，生产项目请改为服务端计算生成，切勿依赖客户端提供的金额结果。
+        public int OrderAmount { get; set; }
+
+        public int RefundAmount { get; set; }
+    }
+}