el-popover 样式修改

el-popover 样式修改 通过popper-class绑定自定义类名popperOptions，
注意popperOptions需放在样式的根文件中
原始样式：

更改后的样式：

<el-popover
      width="300"
      trigger="hover"
      popper-class="popperOptions"
      placement="top-start"
   >
     <div class="operate-btn"  slot="reference">
       <el-badge :value="12" class="item">
         <i class="icon el-icon-chat-line-round">i>
       el-badge>
     div>
     <span slot="default">
       你有99条未读消息，请及时查看
     span>
 el-popover>

.popperOptions[x-placement^=left] .popper__arrow::after{
  border-left-color: #EA4E3D;
}
.popperOptions[x-placement^=right] .popper__arrow::after{
  border-right-color: #EA4E3D;
}
.popperOptions[x-placement^=bottom] .popper__arrow::after{
  border-bottom-color: #EA4E3D;
}
.popperOptions[x-placement^=top] .popper__arrow::after{
  border-top-color: #EA4E3D;
}
.popperOptions {
  background-color: #EA4E3D;
  color: #FFFFFF;
  font-size: 18px;
  padding: 5px;
  border: #EA4E3D;
}