docs/_includes/breadcrumbs.html

{% if page.parent or page.grand_parent %}
<nav class="breadcrumbs" aria-label="Breadcrumb">
  <a href="{{ '/' | relative_url }}">Home</a>
  <span class="sep">›</span>

  {% if page.grand_parent %}
    {% assign gp_page = site.pages | where: "title", page.grand_parent | first %}
    {% if gp_page %}
      <a href="{{ gp_page.url | relative_url }}">{{ page.grand_parent }}</a>
    {% else %}
      <span>{{ page.grand_parent }}</span>
    {% endif %}
    <span class="sep">›</span>
  {% endif %}

  {% if page.parent %}
    {% assign parent_page = site.pages | where: "title", page.parent | first %}
    {% if parent_page %}
      <a href="{{ parent_page.url | relative_url }}">{{ page.parent }}</a>
    {% else %}
      <span>{{ page.parent }}</span>
    {% endif %}
    <span class="sep">›</span>
  {% endif %}

  <span class="current">{{ page.title }}</span>
</nav>
{% endif %}