src/docs/templates/breadcrumbs.html

{%- extends "sphinx_rtd_theme/breadcrumbs.html" %}

{% block breadcrumbs_aside %}
  {% if pagename != 'index' %}
    {{ super() }}
  {% else %}
   <li class="wy-breadcrumbs-aside">
      <a href="https://github.com/apache/couchdb/tree/main/src/docs" class="fa fa-github"> Edit on GitHub</a>
   </li>
  {% endif %}
{% endblock %}