build(rustfmt): add empty rustfmt to ensure project specific settings
see https://github.com/eza-community/eza/commit/4228057db69727785a6efbc78e5b3d22fdbec7ff#commitcomment-138149050 for more info.
Signed-off-by: Christina Sørensen <christina@cafkafk.com>
Christina Sørensen