Highlight focused footnotes

footnotesHighlight.scss

@keyframes highlight {
  0% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}

.footnotes li,
.footnote-ref {
  position: relative;

  &::after {
    position: absolute;
    z-index: -1;
    content: '';
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(
      -100deg,
      rgba(#fae885, 0.3),
      rgba(#fae885, 0.6) 95%,
      rgba(#fae885, 0.1)
    );
    opacity: 0;
  }

  &:target,
  &:focus {
    &::after {
      animation: highlight 2s cubic-bezier(0.3, 0, 1, 0.7);
    }
  }
}