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 (#141)

* 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

* 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>

* chore: Add SPDX-License-Identifier [skip ci]

* add missing SPDX-License-Identifier

* remove unused file

---------

Co-authored-by: Shun Sakai <sorairolake@protonmail.ch>
Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>
Co-authored-by: Chocolate Pie <106949016+chocolate-pie@users.noreply.github.com>

packages/backend/migration/1585385921215-custom-notification.js

@@ -1,4 +1,7 @@
-
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
 
 export class customNotification1585385921215 {
     constructor() {