JSFiddle - React, Tailwind, and code Playground

HTML

<div>HELLO<hr/></div>

CSS

*{
    margin:0;
    padding:0;
}
div{
    position:relative;
    display:inline-block;
}
hr{
    position:absolute;
    top:11px;
    left:0;
    display:inline-block;
    width:100%;
}