JSFiddle - React, Tailwind, and code Playground

HTML

<a href='web+mastodon://follow?uri=acct:gargron@mastodon.social' class='mastodon-intent-btn'>
  <img...

SCSS

@import url('https://fonts.googleapis.com/css?family=Roboto:500');

.mastodon-intent-btn {
  display: inline-block;
  color: #fff;
  text-decoration: none;
  font-size: 14px;
  line-height: 32px;
  font-weight: 500;
  background: #2b90d9;
  border-radius: 4px;
  padding: 0 18px;
  padding-left: 16px;
  font-family: Roboto, sans-serif;
  
  img {
    width: 18px;
    height: 18px;
    vertical-align: middle;
    padding: 12px 0;
    padding-top: 10px;
    margin-right: 5px;
  }
}

JavaScript

[].forEach.call(document.querySelectorAll('.mastodon-intent-btn'), function (el) {
	el.addEventListener('click', function(e) {
    e.preventDefault();
    window.open(e.target.href, 'mastodon-intent', 'width=400,height=400,resizable=no,menubar=no,status=no,scrollbars=yes');
  });
});