perf: replace jQuery with Vanilla JS (#1681)

Also replaced `magnific-popup` with `GLightbox`

_javascript/modules/components/mode-watcher.js

@@ -1,21 +1,14 @@
 /**
  * Add listener for theme mode toggle
  */
-const $toggleElem = $('.mode-toggle');
+const toggle = document.getElementById('mode-toggle');
 
 export function modeWatcher() {
-  if ($toggleElem.length === 0) {
+  if (!toggle) {
     return;
   }
 
-  $toggleElem.off().on('click', (e) => {
-    const $target = $(e.target);
-    let $btn =
-      $target.prop('tagName') === 'button'.toUpperCase()
-        ? $target
-        : $target.parent();
-
-    modeToggle.flipMode(); // modeToggle: `_includes/mode-toggle.html`
-    $btn.trigger('blur'); // remove the clicking outline
+  toggle.addEventListener('click', () => {
+    modeToggle.flipMode();
   });
 }