Setting up REUSE: add copyright statements to j2 and md files in roles/custom/

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

roles/custom/matrix-client-cinny/templates/nginx.conf.j2

@@ -1,3 +1,9 @@
+{#
+SPDX-FileCopyrightText: 2024 MDAD Team and contributors
+
+SPDX-License-Identifier: AGPL-3.0-or-later
+#}
+
 #jinja2: lstrip_blocks: "True"
 # This is a custom nginx configuration file that we use in the container (instead of the default one),
 # because it allows us to run nginx with a non-root user.