Update README.md

README.md

@@ -9,6 +9,7 @@
 [![npm package](https://img.shields.io/npm/v/antd.svg?style=flat-square)](https://www.npmjs.org/package/antd)
 [![NPM downloads](http://img.shields.io/npm/dm/antd.svg?style=flat-square)](https://npmjs.org/package/antd)
 [![Dependency Status](https://david-dm.org/ant-design/ant-design.svg?style=flat-square)](https://david-dm.org/ant-design/ant-design)
+[![Average time to resolve an issue](http://isitmaintained.com/badge/resolution/ant-design/ant-design.svg)](http://isitmaintained.com/project/ant-design/ant-design "Average time to resolve an issue")
 [![Join the chat at https://gitter.im/ant-design/ant-design](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/ant-design/ant-design?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 An enterprise-class UI design language and React-based implementation.