Merge pull request #200 from canonical/h3-toc

Include h3 to table of contents

examples/document.html

@@ -143,7 +143,14 @@ <h4 class="p-table-of-contents__header">On this page</h4>
             <nav class="p-table-of-contents__nav" aria-label="Table of contents">
               <ul class="p-table-of-contents__list">
                 {% for heading in document.headings_map %}
-                <li class="p-table-of-contents__item"><a class="p-table-of-contents__link" href="#{{ heading.heading_slug }}">{{ heading.heading_text }}</a></li>
+                  <li class="p-table-of-contents__item"><a class="p-table-of-contents__link" href="#{{ heading.heading_slug }}">{{ heading.heading_text }}</a></li>
+                  {% if heading.children %}
+                    <ul class="p-table-of-contents__list">
+                    {% for child in heading.children %}
+                      <li class="p-table-of-contents__item"><a class="p-table-of-contents__link" href="#{{ child.heading_slug }}">{{ child.heading_text }}</a></li>
+                      {% endfor %}
+                    </ul>
+                  {% endif %}
                 {% endfor %}
               </ul>
             </nav>