perf: speed up page rendering and jekyll build process (#2034)

- Ensure inline scripts execute after the DOM has fully loaded.
- Use Rollup to bundle the theme-mode and Mermaid scripts, reducing the number of Jekyll include snippets.

_includes/analytics/cloudflare.html

@@ -4,4 +4,3 @@
   src="https://static.cloudflareinsights.com/beacon.min.js"
   data-cf-beacon='{"token": "{{ site.analytics.cloudflare.id }}"}'
 ></script>
-<!-- End Cloudflare Web Analytics -->

_includes/analytics/fathom.html

@@ -2,6 +2,5 @@
 <script
   src="https://cdn.usefathom.com/script.js"
   data-site="{{ site.analytics.fathom.id }}"
-  defer>
-</script>
-<!-- End Fathom Code -->
+  defer
+></script>

_includes/analytics/google.html

@@ -1,7 +1,7 @@
 <!-- Global site tag (gtag.js) - Google Analytics -->
 <script defer src="https://www.googletagmanager.com/gtag/js?id={{ site.analytics.google.id }}"></script>
 <script>
-  document.addEventListener('DOMContentLoaded', function (event) {
+  document.addEventListener('DOMContentLoaded', () => {
     window.dataLayer = window.dataLayer || [];
     function gtag() {
       dataLayer.push(arguments);

_includes/analytics/matomo.html

@@ -1,14 +1,13 @@
 <!-- Matomo -->
-<script type="text/javascript">
-  var _paq = window._paq = window._paq || [];
-  _paq.push(['trackPageView']);
-  _paq.push(['enableLinkTracking']);
-  (function() {
+<script>
+  document.addEventListener('DOMContentLoaded', () => {
+    var _paq = (window._paq = window._paq || []);
+    _paq.push(['trackPageView']);
+    _paq.push(['enableLinkTracking']);
     var u="//{{ site.analytics.matomo.domain }}/";
     _paq.push(['setTrackerUrl', u+'matomo.php']);
     _paq.push(['setSiteId', {{ site.analytics.matomo.id }}]);
     var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
     g.type='text/javascript'; g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s);
-  })();
+  });
 </script>
-<!-- End Matomo Code -->