DRAFT: add deploy sub-command invoking docker stack deploy

[KiaraGrouwstra]

as per my curiosity toward docker stack/swarm stemming from their support for external / long-syntax secrets, i tried my hand at a quick implementation adding a deploy sub-command invoking docker stack deploy. my implementation here is kinda hacky, so this may need some more eyes.

that said, stack deploy seems the primary command in docker stack/swarm involving the compose file arion manages thru nix, so one could as well just invoke their remaining commands directly.