@xiee/utils/css/code-line-numbers.css

Miscellaneous tools and utilities to manipulate HTML pages

span[data-line-number]::before {
  content: attr(data-line-number);
  padding-right: .5em;
  margin-right: 1em;
  display: inline-block;
  border-right: solid 1px;
  color: #ccc;
}