Add license information to files for appservice-double-puppet

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

roles/custom/matrix-appservice-double-puppet/templates/registration.yaml.j2

@@ -1,3 +1,9 @@
+{#
+SPDX-FileCopyrightText: 2024 Slavi Pantaleev
+
+SPDX-License-Identifier: AGPL-3.0-or-later
+#}
+
 # The ID doesn't really matter, put whatever you want.
 id: {{ matrix_appservice_double_puppet_registration_id | to_json }}
 # The URL is intentionally left empty (null), as the homeserver shouldn't