pre-commit hooks

[xmnlab]

Maybe would be good to add a git pre-commit hook for pymapd.

• initially it could run flake8 and black, so the files would be formatted automatically and checked if the format is OK
• also we can add it to CI, so instead to run just flake8, CI can run pre-commit and check if the commit passes for the pre-commit check (black and flake8)

PROS: it helps a lot the development workflow and also the review workflow.

In follow up PRs we can add other pre-commit hooks like isort, mypy or any other service that makes sense for pymapd.

if it is useful for pymapd I can open a PR.