Proposal: `shadowenv -C $dir`

[burke]

I propose adding -C|--change-dir to Shadowenv, which would change to the indicated directory before executing the command. Behaviour per command:

• shadowenv help: no obvious change
• shadowenv init: no obvious change
• shadowenv hook: evaluate the shadowlisp from the indicated directory rather than the current one.
• shadowenv trust: trust the ./.shadowenv.d from the indicated directory rather than the current one.
• shadowenv exec: Change to the indicated directory before loading the environment and executing the indicated process.
• shadowenv diff: unclear. Probably none? Conceivably we could apply the environment changes indicated by the directory's shadowlisp first.

Example usage:

shadowenv -C /my/project exec irb

---

I don't actually have any need motivating this, but I think it'd be a nice, obvious, and relatively simple feature.

[GustavoCaso]

I can tackle this one