This commit adds copyright attributions in SPDX to the files for matrix-client-fluffychat, following REUSE's specification.

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

`-t` works on both old and new Docker versions, so it's best to use that.

* add FluffyChat

* capitalization

* Update group_vars/matrix_servers

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* fix link in readme

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Co-authored-by: Slavi Pantaleev <slavi@devture.com>