ci: add automated testing

[AngryMaciek]

I assume that the files at zonodo together with the go_annotations and theta_annotations make up a test input data? If so, it would we be good to include the script to download the test input data (see #4) as well as expected output.

Having that test data ready:

Since this is a public repo unlimited minutes of GitHub Actions for CI/CD are available!
Iit would be very nice to set up a simple GH Actions workflow which would trigger a testrun with every commit being pushed or every merge request being issued. You can take a look at an example CI/CD workflow here.

[AngryMaciek]

For every GH Action you can have a GH shield too and put it on top of the README. They automatically change colors and text depending on wheter the CI workflow is passing/failing. If you include automated testing in this repo remember to add a test shield as well!