wip(js): add head.html and assets/js

assets/js/modules/layouts/sidebar.js

@@ -0,0 +1,19 @@
+const ATTR_DISPLAY = 'sidebar-display';
+const $sidebar = document.getElementById('sidebar');
+const $trigger = document.getElementById('sidebar-trigger');
+const $mask = document.getElementById('mask');
+
+class SidebarUtil {
+  static #isExpanded = false;
+
+  static toggle() {
+    this.#isExpanded = !this.#isExpanded;
+    document.body.toggleAttribute(ATTR_DISPLAY, this.#isExpanded);
+    $sidebar.classList.toggle('z-2', this.#isExpanded);
+    $mask.classList.toggle('d-none', !this.#isExpanded);
+  }
+}
+
+export function initSidebar() {
+  $trigger.onclick = $mask.onclick = () => SidebarUtil.toggle();
+}