Update .github directory: add copyright information

- Exclude renovate.json
- Rename reuse.toml: capitalization

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

.github/workflows/close-stale-issues.yml

@@ -1,3 +1,7 @@
+# SPDX-FileCopyrightText: 2024 Suguru Hirahara
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 ---
 name: 'Close stale issues and PRs'
 on:  # yamllint disable-line rule:truthy