[no ci] docs: add breadcrumbs for easier navigation

Author: vpratz

docsrc/source/_static/custom.css

@@ -20,3 +20,8 @@
 .bd-sidebar-primary div#rtd-footer-container {
   margin: 0;
 }
+
+ul.bd-breadcrumbs {
+  margin-top: -1rem;
+  margin-bottom: 0.5rem;
+}

docsrc/source/_templates/layout.html

@@ -0,0 +1,10 @@
+{% extends "sphinx_book_theme/layout.html" %}
+
+{% block docs_body %}
+{# This is empty and only shows up if text has been highlighted by the URL #}
+  {% include "components/searchbox.html" %}
+  <article class="bd-article">
+{% include "pydata_sphinx_theme/components/breadcrumbs.html" %}
+    {% block body %}{% endblock %}
+  </article>
+{% endblock docs_body %}