message: fix the headings with permalinks.
  Fixes
diff: h4,
  h5,
  h6 {
  - @apply flex items-center;
  -
  .icon-link {
  - display: flex;
  - align-items: center;
  - margin-left: 0.5rem;
  + @apply inline-block ml-2;
  &::after {
  content: "";
  - display: inline-block;
  - height: 1.4rem;
  - width: 1.4rem;
  + @apply inline-block opacity-0 bg-cover;
  + width: 22px;
  + height: 18px;
  background-image: url("/svg/headling-link.svg");
  - background-size: cover;
  - opacity: 0;
  transition: all 0.2s 50ms;
  }
  }
  &:focus,
  &:hover {
  .icon-link::after {
  - opacity: 1;
  + @apply opacity-100;
  }
  }
  }
  