vue-cli3 引入 font-awesome的操作

[class^="el-icon-fa"], [class*=" el-icon-fa"] {
  display: inline-block;
  font: normal normal normal 14px/1 FontAwesome!important;
  font-size: inherit;
  text-rendering: auto;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
 }
 @import '../node_modules/font-awesome/css/font-awesome.css';
 $fa-css-prefix: el-icon-fa;

 <i class="fa fa-user"></i>
    <i class="fa fa-tree"></i>
    <el-button icon="el-icon-fa fa-user" size="mini">用户</el-button>
    <el-button icon="el-icon-fa fa-tree" size="mini">用户</el-button>