Reinstate jquery

docs/overrides/main.html

@@ -0,0 +1,8 @@
+{% extends "base.html" %}
+
+{% block site_meta %}
+<!-- Place this tag in your head or just before your close body tag. -->
+<script async defer src="https://buttons.github.io/buttons.js"></script>
+<script src="https://code.jquery.com/jquery-3.4.1.min.js"
+  integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
+{% endblock %}