♻️ Move home switcher JS to external file

exampleSite/content/_index.md

@@ -16,8 +16,8 @@ This is a demo site built entirely using Congo. It also contains a complete set
   <span class="flex items-center justify-between grow dark:text-neutral-300">
     <span class="prose dark:prose-invert">This is a demo of the <code id="layout">page</code> layout.</span>
     <button
+      id="switch-layout-button"
       class="px-4 !text-neutral !no-underline rounded-md bg-primary-600 hover:!bg-primary-500 dark:bg-primary-800 dark:hover:!bg-primary-700"
-      onclick="switchLayout()"
     >
       Switch layout &orarr;
     </button>