This commit adds copyright attributions in SPDX to the files for matrix-cactus-comments and matrix-cactus-comments-client, following REUSE's specification. Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
This is split out from matrix-cactus-comments (see 241779b583a4730c), but also heavily inspired by `matrix-static-files`.