feat: implement collapsible sidebar

chore: basic sidebar toggle button
chore: update compiled css

assets/js/sidebar.js

@@ -0,0 +1,12 @@
+document.addEventListener("DOMContentLoaded", function () {
+  const buttons = document.querySelectorAll(".hextra-sidebar-collapsible-button");
+  buttons.forEach(function (button) {
+    button.addEventListener("click", function (e) {
+      e.preventDefault();
+      const list = button.parentElement.parentElement;
+      if (list) {
+        list.classList.toggle("open")
+      }
+    });
+  });
+});