docs: update readme

BiYuqi · BiYuqi · commit a1df26a3d3fe · 2021-02-19T23:13:11.000+08:00
diff --git a/README.md b/README.md
@@ -131,7 +131,7 @@ npm install --save intersection-observer
 
 ## What does IntersectionObserver do?
 
-! [](http://loadingmore-1254319003.coscd.myqcloud.com/observe.png)
+![](http://loadingmore-1254319003.coscd.myqcloud.com/observe.png)
 
 ## Why use this component?
 
