Add testing script and github workflow

[jarzec]

A proposed implementation of #150.

[hsutter]

Thanks! I am definitely interested in CI, but not just yet because I'm trying to keep dependencies a minimal as possible at this stage, plus honestly I don't understand this yet and at this early partial incubation stage I want to keep the contents of this repro to things I can maintain myself. Sorry! but in the future if this goes past the personal incubation stage it will be time to add things like CI for sure. Thanks for understanding!

[stefanofiorentino]

@jarzec here is my fork with both cmake (only for regression-tests for now) and basic CI (only for ubuntu-latest now). As this is not the main target of @hsutter, I'll keep it on my fork and not opening any PR for this. Feel free to have a look and judge anyway :)