Hey @tom-andersson et al - just a maintenance-related PR for your perusal, feel free to reject if this isn't your thing.

What this PR does

• resolves Potential new feature: ruff linting #109
• replaces black with ruff as the linter of choice, partially because of extra features such as linting docstrings in google-style (which black may do as well, but I haven't been able to find it)
• adds pre-commit and a pre-commit config to run the ruff linter and formatter on a pre-commit hook.
• adds info to CONTRIBUTING.md detailing the use of these tools.

What this PR doesn't do

• actually formatting the codebase with ruff so far in this branch to avoid the massive diff
• add a pull request template to remind contributors to follow these steps (that will follow in another PR)

At the moment the CI check fails since ruff is checking all the docstrings, we may be able to soften the docstring rules (configured in pyproject.toml) to something we agree with (e.g. I don't necessarily think that every module needs a docstring)

FYI @nilsleh