MDL-21695 adding help strings

lang/en/moodle.php

@@ -1051,8 +1051,11 @@
 $string['messagedselectedusers'] = 'Selected users have been messaged and the recipient list has been reset.';
 $string['messagedselectedusersfailed'] = 'Something went wrong while messaging selected users.  Some may have received the email.';
 $string['messageprovider:errors'] = 'Important errors with the site';
+$string['messageprovider:errors_help'] = 'These are important errors that an administrator should know about.';
 $string['messageprovider:notices'] = 'Notices about minor problems';
+$string['messageprovider:notices_help'] = 'These are notices that an administrator might be interested in seeing.';
 $string['messageprovider:instantmessage'] = 'Personal messages between users';
+$string['messageprovider:instantmessage_help'] = 'This section configures what happens to messages that are sent to you directly from other users on this site.';
 $string['messageselect'] = 'Select this user as an email recipient';
 $string['messageselectadd'] = 'Add / send message';
 $string['metaaddcourse'] = 'Add this course';