Added hamburger menu for narrow devices

public_html/js/menu.js

@@ -0,0 +1,27 @@
+const hamburger = document.querySelector('.hamburger');
+const mainNav = document.querySelector('#main_menu');
+const hamburgerIcon = document.querySelector('.hamburger_icon');
+const closeIcon = document.querySelector('.close_icon');
+
+hamburger.addEventListener('click', function() {
+    const isOpen = this.getAttribute('aria-expanded') === 'true';
+
+    this.setAttribute('aria-expanded', !isOpen);
+    
+    mainNav.classList.toggle('is_open');
+    hamburgerIcon.classList.toggle('is_open');
+    closeIcon.classList.toggle('is_open');
+
+    if (!isOpen) {
+        const firstLink = mainNav.querySelector('a');
+        if (firstLink) firstLink.focus();
+    }
+});
+
+document.addEventListener('keydown', function(e) {
+    if (e.key === 'Escape' && mainNav.classList.contains('is_open')) {
+        mainNav.classList.remove('is_open');
+        hamburger.setAttribute('aria-expanded', 'false');
+        hamburger.focus();
+    }
+});