fix(navbar): submenus not properly closing on mobile

Instead of properly closing the submenus on mobile, they would shift left and
still be usable. This has been addressed by improved element targeting and the
inclusion of the `touchstart` event.

public/js/navbar.js

@@ -1,14 +1,16 @@
 // Handle submenus
-$('li.dropdown-submenu [data-toggle=dropdown]').on('click', function(event) {
+$('li.dropdown-submenu > [data-toggle=dropdown]').on('click touchstart', function(event) {
     event.preventDefault();
     event.stopPropagation();
 
+    var parent = $(this).parent();
+
     // Also update aria-expanded for accessibility purposes.
-    if ($(this).parent().hasClass('open')) {
-        $(this).parent().removeClass('open');
+    if (parent.hasClass('open')) {
+        parent.removeClass('open');
         $(this).attr('aria-expanded', 'false');
     } else {
-        $(this).parent().addClass('open');
+        parent.addClass('open');
         $(this).attr('aria-expanded', 'true');
     }
 });