{# Table of contents: a nested list of the page's h2-h4 headings. #}
{% macro toc_list(entries) %}
<ul>
  {% for e in entries %}
  <li>
    <a href="#{{ e.id }}">{{ e.title }}</a>
    {% if e.children %}
    {{ toc_list(e.children) }}
    {% endif %}
  </li>
  {% endfor %}
</ul>
{% endmacro %}

{% macro toc(entries) %}
{% if entries | length >= 2 %}
<details class="toc" open>
  <summary>Contents</summary>
  {{ toc_list(entries) }}
</details>
{% endif %}
{% endmacro %}