docs(readme): add Greenkeeper badge

Author: greenkeeper[bot]

README.md

@@ -1,6 +1,8 @@
 
 # React-hooky
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/cloudever/react-hooky.svg)](https://greenkeeper.io/)
+
 ## Why
 
 Since the presentation of hooks in React, many packages have been published for various purposes, and in order not to pull many new dependencies, most of them are combined in this package through re-export