Clarify maintenance mode behavior

Refs https://youtu.be/JztbNGfi_Qk?t=9m38s

modules/cms/lang/en/lang.php

@@ -94,7 +94,8 @@ return [
         'settings_menu' => 'Maintenance mode',
         'settings_menu_description' => 'Configure the maintenance mode page and toggle the setting.',
         'is_enabled' => 'Enable maintenance mode',
-        'is_enabled_comment' => 'When activated website visitors will see the page chosen below.'
+        'is_enabled_comment' => 'Select the page to show when maintenance mode is activated.',
+        'hint' => 'Maintenance mode will display the maintenance page to visitors who are not signed in to the back-end area.',
     ],
     'page' => [
         'not_found_name' => "The page ':name' is not found",

modules/cms/models/maintenancesetting/_hint.htm

@@ -0,0 +1,4 @@
+
+<p>
+    <?= e(trans('cms::lang.maintenance.hint')) ?>
+</p>

modules/cms/models/maintenancesetting/fields.yaml

@@ -4,6 +4,10 @@
 
 fields:
 
+    hint:
+        type: hint
+        path: ~/modules/cms/models/maintenancesetting/_hint.htm
+
     is_enabled:
         label: cms::lang.maintenance.is_enabled
         comment: cms::lang.maintenance.is_enabled_comment