Convert ot MR

Closes #3228418

config/install/extlink.settings.yml

@@ -11,6 +11,7 @@ extlink_alert_text: 'This link will take you to an external web site. We are not
 extlink_hide_icons: false
 extlink_additional_link_classes: ''
 extlink_additional_mailto_classes: ''
+extlink_additional_tel_classes: ''
 extlink_exclude: ''
 extlink_include: ''
 extlink_class: 'ext'
@@ -20,6 +21,8 @@ extlink_css_exclude: ''
 extlink_css_explicit: ''
 extlink_mailto_class: 'mailto'
 extlink_mailto_label: '(link sends email)'
+extlink_tel_class: 'tel'
+extlink_tel_label: '(link is a phone number)'
 extlink_use_font_awesome: false
 extlink_font_awesome_classes: {  }
 extlink_icon_placement: 'append'