docs: migrate to google tag manager (#4711)

docs/_theme/djangodocs/basic/layout.html

@@ -138,6 +138,13 @@
     {%- block scripts %}
     {{- script() }}
     {%- endblock %}
+    <!-- Google Tag Manager -->
+    <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+    new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+    j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+    'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+    })(window,document,'script','dataLayer','GTM-PF5MQ2Z');</script>
+    <!-- End Google Tag Manager -->
     {%- if use_opensearch %}
     <link rel="search" type="application/opensearchdescription+xml"
           title="{% trans docstitle=docstitle|e %}Search within {{ docstitle }}{% endtrans %}"
@@ -174,6 +181,10 @@
 {%- block content %}
   {%- block sidebar1 %} {# possible location for sidebar #} {% endblock %}
 
+    <!-- Google Tag Manager (noscript) -->
+    <noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-PF5MQ2Z"
+    height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
+    <!-- End Google Tag Manager (noscript) -->
     <div class="document">
   {%- block document %}
       <div class="documentwrapper">

docs/_theme/djangodocs/layout.html

@@ -168,17 +168,6 @@
 {% block sidebar2 %}{% endblock %}
 {% block footer %}
 
-  <!-- GA -->
-  <script>
-    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-        (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
-      m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
-    })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');
-
-    ga('create', 'UA-59768903-1', 'auto');
-    ga('send', 'pageview');
-  </script>
-
   <!-- intercom -->
   <script>
     window.intercomSettings = {
@@ -259,16 +248,14 @@
 
     // Track GA event
     const trackga = function ( category, action, label, value ) {
-      // If ga is available
-      if ( ga ) {
-        ga('send', {
-          hitType: 'event',
-          eventCategory: category,
-          eventAction: action,
-          eventLabel: label,
-          eventValue: value
-        });
-      }
+      window.dataLayer = window.dataLayer || [];
+      window.dataLayer.push({
+        event: 'Click Events',
+        category: category,
+        action: action,
+        label: label,
+        value: value
+      })
     };
   </script>