不借助 <el-scrollbar> 这种标签，实现滚动条的效果

一、使用 <div> 标签，设置 height:700px; overflow:auto;

二、<el-main> 标签，设置：

.el-main{
  height: 600px;
  overflow-x: hidden;
  overflow-y: scroll;
  &::-webkit-scrollbar {
    position: absolute;
    width: 4px;
    right: 2px;
    bottom: 2px;
    z-index: 1;
    border-radius: 4px;
    opacity: 0;
    -webkit-transition: opacity 120ms ease-out;
    transition: opacity 120ms ease-out;
  }
  &::-webkit-scrollbar-thumb {
    position: relative;
    display: block;
    cursor: pointer;
    border-radius: 4px;
    background-color: rgba(144, 147, 153, 0.3);
    transition: 0.3s background-color;
    &:hover{
      background-color: rgba(144, 147, 153, 0.5);
    }
  }
}

隐藏掉 水平滚动条 ：wrap-style="overflow-x: hidden;"