dialog的title下面加个下划线

   <el-dialog
  :title="title"
  :visible.sync="open"
  class="alertlablefixtitle"
  width="500px"
  append-to-body
  :close-on-click-modal="false"
>
   
   
   
   .alertlablefixtitle .el-dialog__header {
      border-bottom: gainsboro 1px solid;
    }