add npm@next version badge

README.md

@@ -7,6 +7,7 @@
 Wechaty is a Bot SDK for Wechat **Personal** Account which can help you create a bot in 6 lines of javascript, with cross-platform support include [Linux](https://travis-ci.com/chatie/wechaty), [Windows](https://ci.appveyor.com/project/chatie/wechaty), [Darwin(OSX/Mac)](https://travis-ci.com/chatie/wechaty) and [Docker](https://app.shippable.com/github/Chatie/wechaty).
 
 [![NPM Version](https://badge.fury.io/js/wechaty.svg)](https://badge.fury.io/js/wechaty)
+[![npm (tag)](https://img.shields.io/npm/v/wechaty/next.svg)](https://www.npmjs.com/package/wechaty?activeTab=versions)
 [![Downloads](https://img.shields.io/npm/dm/wechaty.svg?style=flat-square)](https://www.npmjs.com/package/wechaty)
 [![GitHub stars](https://img.shields.io/github/stars/Chatie/wechaty.svg?label=github%20stars)](https://github.com/chatie/wechaty)
 [![Docker Pulls](https://img.shields.io/docker/pulls/zixia/wechaty.svg?maxAge=2592000)](https://hub.docker.com/r/zixia/wechaty/)