foo.be/_includes/footer.html

<footer class="c-footer">
  <div class="u-container c-footer__container">
    <p>&copy; Alexandre Dulaunoy - licensed under the version 2 of the GNU General Public License or any later version.</p>
    <p>
      {% if site.twitterUsername %}<a href="https://twitter.com/{{ site.twitterUsername }}">Twitter</a>{% endif %}
      {% if site.githubUsername %}<a href="https://github.com/{{ site.githubUsername }}">Github</a>{% endif %}
      {% if site.flickrUsername %}<a href="https://flickr.com/photos/{{ site.flickrUsername }}">Flickr</a>{% endif %}
      <a rel="me" href="https://infosec.exchange/@adulau">Mastodon (infosec)</a>
      <a rel="me" href="https://paperbay.org/@a">Mastodon (the other side)</a>
      <a ref="me" href="https://git.foo.be/adulau">git.foo.be</a>
    </p>
  </div>
</footer>