Adds a very simple bootstrap script for setting up a new host. I'm not
exactly sure the best way to use this yet. Though I suppose it could be
run with some sort of "curl https://blahblah | bash" shenanigans. That
just seems like it would be about as much effort as just running the
nixos-rebuild command itself from a new host.
In any case though, this worked well for bootstrapping a new wixos
instance. So that was nice.
