Add CI to run unity tests

[ammaraskar]

This will run the tests on a github action for pull requests. You can see an example run here: https://github.com/ammaraskar/OpenTS2/actions/runs/3645531478/jobs/6155795438

You will need to add your unity license as a secret in the github repo. Instructions are here under the Setting up License section. Basically you need to make a branch with a workflow and manually trigger it, that gives you a file to upload to unity and then you can download your license and add it a secret to the repo.

I'm also just happy to send you my license if you'd like 😅

[LazyDuchess]

Okayyy cool I'm sure I can set it up

[LazyDuchess]

All good!