css添加三角指示器

.bar{
  ...
     &:before {
        top: 100%;
        left: 24px;
        border: solid rgba(0, 0, 0, 0);
        content: '';
        height: 0;
        width: 0;
        position: absolute;
        border-top-color: rgba(68, 65, 65, 0.84);
        border-width: 5px;
        margin-left: -5px;
      }
}