Add license information to files for matrix-registration

This commit adds copyright attributions in SPDX to the files for matrix-registration following REUSE's specification.

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

roles/custom/matrix-registration/tasks/list_tokens.yml

@@ -1,3 +1,9 @@
+# SPDX-FileCopyrightText: 2021 MDAD project contributors
+# SPDX-FileCopyrightText: 2022 Marko Weltzer
+# SPDX-FileCopyrightText: 2022 Slavi Pantaleev
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 ---
 
 - name: Call matrix-registration list all tokens API