Add license information to files for matrix-ma1sd

This commit adds copyright attributions in SPDX format to the files for matrix-ma1sd following REUSE's specification.

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

roles/custom/matrix-ma1sd/vars/main.yml

@@ -1,3 +1,8 @@
+# SPDX-FileCopyrightText: 2020 Marcel Partap
+# SPDX-FileCopyrightText: 2022 Slavi Pantaleev
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 ---
 
 # Doing `|from_yaml` when the extension contains nothing yields an empty string ("").