安装yarn
https://yarnpkg.com/lang/zh-hans/docs/install/
使用国内镜像加速npm和yarn
1. npm config set registry=https://registry.npm.taobao.org
2. yarn config set registry https://registry.npm.taobao.org
3. 下载cnpm：npm install -g cnpm --registry=https://registry.npm.taobao.org
