Add isort to the CI

[Flowrey]

Problem to solve

Imports are not sorted

Proposal

Create a github action to check if import are sorted with isort

Further details

Use isort with the black profile: https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#isort
https://pycqa.github.io/isort/docs/configuration/github_action.html