chore: 著作権とライセンスについての情報を各ファイルに追加する (#11348)

* chore: Add the SPDX information to each file

Add copyright and licensing information as defined in version 3.0 of
the REUSE Specification.

* tweak format

---------

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

healthcheck.sh

@@ -1,4 +1,7 @@
 #!/bin/bash
 
+# SPDX-FileCopyrightText: syuilo and other misskey contributors
+# SPDX-License-Identifier: AGPL-3.0-only
+
 PORT=$(grep '^port:' /misskey/.config/default.yml | awk 'NR==1{print $2; exit}')
 curl -s -S -o /dev/null "http://localhost:${PORT}"