app/views/templates/release_nav.html.twig

  <header class="mx-auto mb-3">
    <h1>
    {% if release > 1 %}
    <a href="?version={{ release -1 }}" title="Previous release" class="text-decoration-none">«</a>
    {% endif %}
      &nbsp;Firefox&nbsp;{{ release }}&nbsp;
      <a href="?version={{ release +1 }}" title="Next release" class="text-decoration-none">»</a><br>
    {% if release != constant('FIREFOX_RELEASE')|number_format %}
      <a href="?version={{ constant('FIREFOX_RELEASE')|number_format }}" class="btn btn-primary">Go to <b>Release</b> channel</a>
    {% endif %}
    </h1>
  </header>