Issue #2308581 by mgifford: Added Document accessibility features in Telephone.

core/modules/telephone/telephone.module

@@ -21,7 +21,7 @@ function telephone_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<dt>' . t('Managing and displaying telephone fields') . '</dt>';
       $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the telephone field can be configured separately. See the <a href="!field_ui">Field UI help</a> for more information on how to manage fields and their display.', array('!field_ui' => \Drupal::url('help.page', array('name' => 'field_ui')))) . '</dd>';
       $output .= '<dt>' . t('Displaying telephone numbers as links') . '</dt>';
-      $output .= '<dd>' . t('Telephone numbers can be displayed as links with the scheme name <em>tel:</em> by choosing the <em>Telephone</em> display format on the <em>Manage display</em> page. Any spaces will be stripped out of the link text.') . '</dd>';
+      $output .= '<dd>' . t('Telephone numbers can be displayed as links with the scheme name <em>tel:</em> by choosing the <em>Telephone</em> display format on the <em>Manage display</em> page. Any spaces will be stripped out of the link text. This semantic markup improves the user experience on mobile and assistive technology devices.') . '</dd>';
       $output .= '</dl>';
       return $output;
   }