send notification on update failure

resources/lang/en-GB/notifications.php

@@ -7,4 +7,21 @@ return [
     'salutation'          => 'Regards,<br> :company_name',
     'subcopy'             => 'If you’re having trouble clicking the ":text" button, copy and paste the URL below into your web browser: [:url](:url)',
 
+    'update' => [
+
+        'mail' => [
+
+            'subject' => '⚠️ Update failed on :domain',
+            'message' => 'The update of :alias from :current_version to :new_version failed in <strong>:step</strong> step with the following message: :error_message',
+
+        ],
+
+        'slack' => [
+
+            'message' => 'Update failed on :domain',
+
+        ],
+
+    ],
+
 ];