Add basic test and CI

[RangerMauve]

Is your feature request related to a problem? Please describe.

We don't know whether updating expo would break things. It'd be nice to have even a basic signal that stuff is still working.

Describe the solution you'd like

I think we should have a simple test using tape which we can run via the CI the way we would other libraries and use Github Actions to run it on changes

Describe alternatives you've considered

Having more in-depth unit tests, which would be nice but would take way more time

Additional context