Add a unit tests pipeline

[ctmbl]

Now that the project is growing well, it might be a good thing to implement a unit test (or are you never experiencing bus 🙃 ?) pipeline that needs to pass before each merge.

That would also require to write some unit tests but the task could be accomplished smoothly by adding tests only related to new modifications (of bug fix), with some time the test suite should reach a pretty good code coverage 👍

I'd like to have the main contributors point of view about that to know if it's worth working on something!