Add license information to files for matrix-bot-mjolnir

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

roles/custom/matrix-bot-mjolnir/tasks/setup_uninstall.yml

@@ -1,3 +1,10 @@
+# SPDX-FileCopyrightText: 2021 - 2022 Slavi Pantaleev
+# SPDX-FileCopyrightText: 2021 Aaron Raimist
+# SPDX-FileCopyrightText: 2022 Marko Weltzer
+# SPDX-FileCopyrightText: 2022 Sebastian Gumprich
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 ---
 
 - name: Check existence of matrix-bot-mjolnir service