JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

ol {
  counter-reset: section;
  list-style-type: none;
}     
ol li { counter-increment: section; }
            
ol li:before  { content: counters(section, ".") ". "; }