Update 'README.md'

README.md

@@ -2,3 +2,10 @@
 
 左右滑动删除效果demo
 
+## preview
+
+![](https://file.yoqi.me/Developer/Flutter/flutter_slidable_demo/%E5%8A%A8%E7%94%BB%20(25).gif)
+
+## download it
+
+[flutter_slidable_demo_1.0.0.apk](http://fileshare.takegpt.cn/downloads/Flutter/flutter_slidable_demo)