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/head.html

@@ -97,11 +97,32 @@
     <link rel="stylesheet" href="{{ site.data.origin[type].glightbox.css | relative_url }}">
   {% endif %}
 
-  <!-- JavaScript -->
+  <!-- Scripts -->
 
   {% unless site.theme_mode %}
-    {% include mode-toggle.html %}
+    <script src="{{ '/assets/js/dist/theme.min.js' | relative_url }}"></script>
   {% endunless %}
 
+  {% include js-selector.html lang=lang %}
+
+  {% if jekyll.environment == 'production' %}
+    <!-- PWA -->
+    {% if site.pwa.enabled %}
+      <script
+        defer
+        src="{{ '/app.min.js' | relative_url }}?baseurl={{ site.baseurl | default: '' }}&register={{ site.pwa.cache.enabled }}"
+      ></script>
+    {% endif %}
+
+    <!-- Web Analytics -->
+    {% for analytics in site.analytics %}
+      {% capture str %}{{ analytics }}{% endcapture %}
+      {% assign platform = str | split: '{' | first %}
+      {% if site.analytics[platform].id and site.analytics[platform].id != empty %}
+        {% include analytics/{{ platform }}.html %}
+      {% endif %}
+    {% endfor %}
+  {% endif %}
+
   {% include metadata-hook.html %}
 </head>