JSFiddle - React, Tailwind, and code Playground

HTML

<footer>
  <div class="copyright">Copyright 2019</div>
</footer>

CSS

* {
  box-sizing: border-box;
}
body {
  margin: 0;
  padding: 0;
}
footer {
  width: 100%;
  background-color: #333;
  padding: 15px;
}
footer .copyright {
  width: 100%;
  text-align: center;
  color: #fff;
}
footer .copyright::before {
  content: '';
  width: 100%;
  height: 1px;
  display: block;
  background-color: #fff;
  margin-bottom: 10px;
}