JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>blabla</li>
    <li>blablabla</li>
    <li><span>et pourtant</span>
       <ul>
          <li>ouiouioui</li>
          <li>nononon</li>
       </ul>
    </li>
</ul>

CSS

span {border-bottom:1px solid red;width:100%;display:inline-block}
ul {width:100%} 
ul ul {margin:0 0 0 20px}