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.

_javascript/modules/layouts/basic.js

@@ -1,7 +1,7 @@
-import { back2top } from '../components/back-to-top';
-import { loadTooptip } from '../components/tooltip-loader';
+import { back2top, loadTooptip, modeWatcher } from '../components';
 
 export function basic() {
+  modeWatcher();
   back2top();
   loadTooptip();
 }