docs: add ChunkedBodyWriter effect display (#807)

Author: chaoranz758

content/en/docs/hertz/tutorials/framework-exten/response_writer.md

@@ -71,3 +71,11 @@ time.Sleep(200 * time.Millisecond)
 }
 })
 ```
+
+Effect display:
+
+Open the interface in the example at localhost:8888, and then use the following command to observe the effect:
+
+```bash 
+curl -N --location localhost:8888//flush/chunk
+```

content/zh/docs/hertz/tutorials/framework-exten/response_writer.md

@@ -62,3 +62,11 @@ Hertz 在 `app.RequestContext` 中提供了 `Response.HijackWriter` 方法让用
 		}
 	})
 ```
+
+效果展示：
+
+在 localhost:8888 开启示例中的接口，然后使用如下命令观察效果：
+
+```bash 
+curl -N --location localhost:8888//flush/chunk
+```