Add menu hide/show toggle on mobile

src/servala/frontend/templates/frontend/base.html

@@ -20,6 +20,11 @@
     <div id="app">
         {% include 'includes/sidebar.html' %}
         <div id="main">
+            <header class="mb-3">
+                <a href="#" class="burger-btn d-block d-xl-none">
+                    <i class="bi bi-justify fs-3"></i>
+                </a>
+            </header>
             <div class="page-heading">
                 <h3>
                     {% block page_title %}