border 길이 설정

import { css } from "styled-components";

export const mixinBorder = css`
  position: relative;
  :after {
    content: "";
    position: absolute;
    bottom: 0;
    left: 13px;
    height: 1px;
    width: calc(100% - 13px * 2); /* 길이 설정 */
    border-bottom: 1px dotted black;
  }
`;

참고: https://stackoverflow.com/questions/4131490/any-way-to-limit-border-length