Add ratings icons to AO3

ao3-ratings.css

dd.rating a::before {
  color: #fff;
  padding: 0 1ex;
  margin-right: 1ex;
  border-radius: 0.333ex;
}

dd.rating a[href="/tags/General%20Audiences/works"]::before {
  content: "G";
  background: #78a700;
}

dd.rating a[href="/tags/Teen%20And%20Up%20Audiences/works"]::before {
  content: "T";
  background: #e6d200;
  color: #000;
}

dd.rating a[href="/tags/Mature/works"]::before {
  content: "M";
  background: #ed8115;
}

dd.rating a[href="/tags/Explicit/works"]::before {
  content: "E";
  background: #980000;
}

dd.rating a[href="/tags/Not%20Rated/works"]::before {
  content: "NR";
  background: #999;
}

Screenshots: