Add pre-commit hook configuration for black

This MR adds a pre-commit hook configuration, which runs black on changed files before committing them. This process runs on the development machine and needs to be activated once by each developer, see added documentation.

Solves #1 (closed)

This setup is based on https://dev.to/m1yag1/how-to-setup-your-project-with-pre-commit-black-and-flake8-183k

@alewis Note that for convenience I developed this MR on top of !1 (merged), so we should merge that MR first.