ul.tags {
    list-style-type: none;
}

ul.tags  li {
    padding-left: .5em;
    padding-right: .5em;
    display: inline-block;
}

pre.showlines {
  white-space: pre-wrap;
}
pre.showlines::before {
  counter-reset: listing;
}
pre.showlines code {
  counter-increment: listing;
}
pre.showlines code::before {
  content: counter(listing) ". ";
  display: inline-block;
  width: 3em;         /* now works */
  text-align: right;  /* now works */
}