docs: add demo desc

Author: NelsonYong

packages/hooks/src/useRequest/docs/loadingDelay/index.en-US.md

@@ -15,6 +15,8 @@ By setting `options.loadingDelay`, you can delay the time when `loading` turns t
 
 ### Basic usage
 
+If you hit run quickly, the data without loadingDelay will flash.
+
 <demo src="./demo/demo.vue"
   language="vue"
   title=""

packages/hooks/src/useRequest/docs/loadingDelay/index.zh-CN.md

@@ -15,6 +15,8 @@ source:
 
 ### 基本用法
 
+如果你快速的点击 run, 没使用 loadingDelay 的数据将会闪烁。
+
 <demo src="./demo/demo.vue"
   language="vue"
   title=""