Added a "spell" command to https://github.com/fiatjaf/nak

- `nak req -k 777 -a [email protected] --outbox | jq` to see all @verbiricha spells
- pick one and run `nak req -i c1214b196b3664bc7fc8c8dfaa082a24ed09b25028773bcae60fef8dfe6646fa -a [email protected] --outbox | nak spell --pub fiatjaf.com` to run it in the context of your user (replace 'fiatjaf.com' with your npub or nip05)
- `nak spell` will list your previously used spells with ids that you can use to invoke them again: `nak spell spellcgk4u9c --pub fiatjaf.com`

It's not super useful, but it is something.