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>

packages/frontend/src/style.scss

@@ -1,5 +1,11 @@
 @charset "utf-8";
 
+/*
+ * SPDX-FileCopyrightText: syuilo and other misskey contributors
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
 :root {
 	--radius: 12px;
 	--marginFull: 16px;