a11y for anyone.
Just add the following to any page you want to have this button:
<link rel="stylesheet" href="https://a11y.tservic.es/a11y.css" />
<script src="https://a11y.tservic.es/a11y.js"></script>
Or even better: Host it yourself: https://git.tservic.es/thies/a11y