Update online docs to use GA4

.github/workflows/docs_update.yml

@@ -37,7 +37,7 @@ jobs:
       - name: Customize for online docs
         working-directory: docs/doxygen
         run: |
-          sed -i'' -e "s@<!--EXTRA FOOTER 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)})(window,document,'script','//www.google-analytics.com/analytics.js','ga');ga('create', 'UA-794025-2', 'auto');ga('send', 'pageview');</script>@" \
+          sed -i'' -e "s@<!--EXTRA FOOTER SCRIPT-->@<script async src=\"https://www.googletagmanager.com/gtag/js?id=G-JL42SGJP7H\"></script><script>window.dataLayer=window.dataLayer||[];function gtag(){dataLayer.push(arguments);} gtag('js',new Date()); gtag('config','G-JL42SGJP7H');</script>@" \
             custom_footer.html
 
       - name: Generate documentation