JSFiddle - React, Tailwind, and code Playground

HTML

<ol>
  <li>item 1
    <ol>
      <li>sub item 1
        <ol>
          <li>sub-sub item 1</li>
          <li>sub-sub item 2</li>
          <li>sub-sub item 3</li>
        </ol>
      </li>
      <li>Sub item 2</li>
   </ol>
  </li>
  <li>item 2</li>
</ol>

CSS

ol {
  counter-reset: section;
  list-style-type: none;
}
ol ol ol{background:#c0c0c0; padding-left:10px;}       
ol li { counter-increment: section; }
            
ol li:before  { content: counters(section, ".") ". "; }