Update Contributing.md after pre-commit addition

[thepetk]

/type task

Which area/kind this task is related to?

/type documentation

Task Description

After the implementation of #6 the pre-commit workflow has been added. The workflow might require additional steps for each contributor so their statuses will be successful.

That said the CONTRIBUTING.md (and any other related files) need to be updated.

[thepetk]

@skpanagiotis εδώ δεν θυμάμαι γιατί έχω βάλει το 3.12 mvp milestone να πω την αλήθεια. Δεν νομίζω ότι είναι hard requirement.