Issue #3508199: Navigation Top Bar accessibility issues found by Nightwatch tests

Closes #3508199

core/modules/navigation/templates/top-bar-page-actions.html.twig

@@ -23,6 +23,7 @@
 
 {% include 'navigation:toolbar-button' with {
   icon: 'dots',
+  action: 'More actions'|t,
   attributes: create_attribute(
     {
       'aria-expanded': 'false',