Add GA4 tag script (#175)

_layouts/default.html

@@ -16,7 +16,8 @@
     {% include footer.html %}
 
     <!-- Google Analytics -->
-    <script>
+
+    <!-- <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)
@@ -25,6 +26,16 @@
       ga('create', 'UA-28181852-21', 'auto');
       ga('send', 'pageview');
 
+    </script> -->
+
+    <!-- Google tag (gtag.js) -->
+    <script async src="https://www.googletagmanager.com/gtag/js?id=G-PY71RTY5GV"></script>
+    <script>
+      window.dataLayer = window.dataLayer || [];
+      function gtag(){dataLayer.push(arguments);}
+      gtag('js', new Date());
+
+      gtag('config', 'G-PY71RTY5GV');
     </script>
 
     <script src="/js/site.js"></script>