JSFiddle - React, Tailwind, and code Playground

HTML

<h1><span class="headline">Introduction</span></h1>

CSS

.headline {
font-family: Calibri, "Helvetica", san-serif;
line-height: 1.5em;
color: black;
font-size: 20px;
}
h1:after
{
    content:' ';
    display:block;
    border:2px solid black;
}