3497604_6 Accessibility issue fix rol="img" must have alternative text.

Closes #3497604 Accessibility issue fix rol="img" must have alternative text.

js/extlink.js

@@ -455,6 +455,9 @@
           }
         }
         iconElement.setAttribute('role', 'img');
+        if (!iconElement.getAttribute('aria-label')) {
+          iconElement.setAttribute('aria-label', drupalSettings.data.extlink.extLabel);
+        }
         iconElement.setAttribute('aria-hidden', drupalSettings.data.extlink.extHideIcons);
         link[iconPlacement](iconElement);
       }