Atom - Add line numbers in code block of Asciidoctor-preview

README.adoc

Run Cmd/Ctrl+Shift+P and type : Open your stylesheet

Then add the content of style.less in that file.

style.less

.asciidoc-preview .listingblock pre.editor-colors {
  counter-reset: lines;

  .line {
    counter-increment: lines;
  }

  .line::before {
      content: counter(lines); text-align: right;
      display: inline-block; width: 2em;
      padding-right: 0.5em; margin-right: 0.5em;
      border-right: 1px solid #e0e0e0 !important;
  }
}