Load jquery if isn't found

Sphinx is removing jquery on the 6.x version.
Our theme depends a lot on jquery.

docs/_static/debug.js

@@ -1,7 +1,7 @@
-// Add debug actions to flyout menu
-
-$(function () {
-  $("[data-toggle='rst-debug-badge']").on("click", function () {
+// Add debug actions to flyout menu.
+document.addEventListener("DOMContentLoaded", function () {
+  let element = document.querySelector("[data-toggle='rst-debug-badge']");
+  element.addEventListener("click", function () {
     $("[data-toggle='rst-versions']").toggleClass("rst-badge");
   });
-})
+});

sphinx_rtd_theme/layout.html

@@ -228,8 +228,8 @@
   {% include "versions.html" -%}
 
   <script>
-      jQuery(function () {
-          SphinxRtdTheme.Navigation.enable({{ 'true' if theme_sticky_navigation|tobool else 'false' }});
+      document.addEventListener("DOMContentLoaded", function () {
+        SphinxRtdTheme.Navigation.enable({{ 'true' if theme_sticky_navigation|tobool else 'false' }});
       });
   </script>
 

sphinx_rtd_theme/search.html

@@ -17,7 +17,9 @@
 {%- endblock %}
 {% block footer %}
   <script>
-    jQuery(function() { Search.loadIndex("{{ pathto('searchindex.js', 1) }}"); });
+    document.addEventListener("DOMContentLoaded", function () {
+      Search.loadIndex("{{ pathto('searchindex.js', 1) }}");
+    });
   </script>
   {# this is used when loading the search index using $.ajax fails,
      such as on Chrome for documents on localhost #}

src/theme.js

@@ -1,4 +1,20 @@
-var jQuery = (typeof(window) != 'undefined') ? window.jQuery : require('jquery');
+/**
+ * Inject jquery if isn't present already.
+ *
+ * @param {function} fn - Function to be executed after jquery has been loaded.
+ */
+function injectJQuery(fn) {
+    if (!window.jQuery) {
+        console.log("JQuery not found. Injecting.");
+        var script = document.createElement("script");
+        script.type = 'text/javascript';
+        script.src = "https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js";
+        script.onload = fn;
+        document.head.appendChild(script);
+    } else {
+        fn();
+    }
+}
 
 // Sphinx theme nav state
 function ThemeNav () {
@@ -32,8 +48,8 @@ function ThemeNav () {
         }
 
         self.isRunning = true;
-        jQuery(function ($) {
-            self.init($);
+        injectJQuery(function () {
+            self.init();
 
             self.reset();
             self.win.on('hashchange', self.reset);
@@ -69,7 +85,7 @@ function ThemeNav () {
         this.enable(true);
     };
 
-    nav.init = function ($) {
+    nav.init = function () {
         var doc = $(document),
             self = this;