[tooling] improved kialourl setting description

lang/en/kialo.php

@@ -55,7 +55,7 @@
 $string['kialoname'] = 'Activity Name';
 $string['kialosettings'] = 'Settings';
 $string['kialourl'] = 'Kialo URL';
-$string['kialourl_desc'] = 'The URL of the Kialo instance to use.';
+$string['kialourl_desc'] = 'The URL of the Kialo instance to use. Leave blank to use the default (edu-prod) or to use the value of the TARGET_KIALO_URL environment variable instead.';
 $string['modulename'] = 'Kialo Discussion';
 $string['modulename_help'] = 'The Kialo Discussion activity allows you to include a Kialo discussion in your Moodle course. Students can participate in the discussion directly from Moodle, without having to manually create Kialo accounts. Kialo discussions are a great way to teach and train critical thinking, argumentation and to facilitate thoughtful classroom discussions.';
 $string['modulename_link'] = 'https://support.kialo-edu.com/en/hc/moodle';