ant-design/.dumi/theme/common/styles/HeadingAnchor.tsx

import React from 'react';
import { css, Global } from '@emotion/react';

export default () => (
  <Global
    styles={css`
      h1,
      h2,
      h3,
      h4,
      h5,
      h6 {
        > a[aria-hidden]:first-child {
          float: left;
          width: 20px;
          padding-inline-end: 4px;
          font-size: 0;
          line-height: inherit;
          text-align: right;
          padding-inline-end: 4px;
          margin-inline-start: -24px;

          [data-direction='rtl'] & {
            float: right;
          }

          &:hover {
            border: 0;
          }

          > .icon-link::before {
            font-size: 20px;
            content: '#';
          }
        }

        &:not(:hover) > a[aria-hidden]:first-child > .icon-link {
          visibility: hidden;
        }
      }
    `}
  />
);