point ssh:// to iSH

It's a minor addition, but I think having iSH respond to `ssh://` links by running `ssh` (OpenSSH or not) would be neat. I really think there's some use for this, and if it's not too much hassle, please consider it.

For example, `ssh://nat@ctrl-c.club` would open iSH and run `$ ssh nat@ctrl-c.club`. Ideally, the argument should exclusively be in the *user*@*domain* format, so that `ssh://ctrl-c` is invalid.

Thanks!
~ Natalie