Integrate CodeCov (CI)

[AtilioA]

Could be any other code coverage solution, but I've used CodeCov and can recommend it.
Depends on #27. Both will probably be demanded by JP.

[AtilioA]

@Henriquelay can you make a simple test pipeline as soon as you get the tests set up in a minimally working state (i.e. testing without coverage report)? That should be simple and would technically suffice for the CI requirement, and we would be able to work upon that in the future if we want.