docs: add lerna badge in README [ci skip] (#3627)

Author: armujahid

README.md

@@ -1,4 +1,5 @@
-# vue-cli [![Build Status](https://circleci.com/gh/vuejs/vue-cli/tree/dev.svg?style=shield)](https://circleci.com/gh/vuejs/vue-cli/tree/dev) [![Windows Build status](https://ci.appveyor.com/api/projects/status/rkpafdpdwie9lqx0/branch/dev?svg=true)](https://ci.appveyor.com/project/yyx990803/vue-cli/branch/dev)
+# vue-cli [![Build Status](https://circleci.com/gh/vuejs/vue-cli/tree/dev.svg?style=shield)](https://circleci.com/gh/vuejs/vue-cli/tree/dev) [![Windows Build status](https://ci.appveyor.com/api/projects/status/rkpafdpdwie9lqx0/branch/dev?svg=true)](https://ci.appveyor.com/project/yyx990803/vue-cli/branch/dev) [![lerna](https://img.shields.io/badge/maintained%20with-lerna-cc00ff.svg)](https://lernajs.io/)
+
 
 > Vue CLI is the Standard Tooling for Vue.js Development.