#406: Run pre-commit for black and isort

• Set up cache
• https://pre-commit.com/#usage-in-continuous-integration
• Set Py3.9 as default since pre-commit is installed on Py3.9 image

Close #406 (closed).

changed milestone to %0.10.0

added CI/CD Dev Env labels

approved this merge request

assigned to @moul and unassigned @matograine

merged