在div上添加小三角

&::before{
  width: 0;
  height: 0;
  position: absolute;
  content: "";
  right: 10px;
  top: 9px;
  border-right: 7px dashed transparent;
  border-bottom: 7px solid currentColor;
  border-left: 7px dashed transparent;
}

之后再调样式等