chore: Add SPDX header

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

lib/Event/AclCreatedEvent.php

@@ -1,7 +1,10 @@
 <?php
 
 declare(strict_types=1);
-
+/**
+ * SPDX-FileCopyrightText: 2021 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
 
 namespace OCA\Deck\Event;