bootstrap ci tests

[eightfilms]

Should close #2 for good, because testing is the only missing step.

• bootstrapping with a simple test just so we can get a test CI up and running.
• don't think other areas of the code are valid for testing now, perhaps we might want a more comprehensive test suite (i like cargo's one more than rustup's) once we get more commands up and running

[eightfilms]

marking this as ready for review since I think there's not much else to add for now. It's iffy trying to test filesystem operations, and I don't think it's very useful to test interactions with GitHub.

Hoping to adopt more of a TDD approach when expanding on new features. At some point we should also eventually have integration tests that runs the CLI and calls each command, and assert that the output is fine.

I think we have a good start with just bootstrapping tests in the CI, and this PR accomplished that goal.