Integrate code quality tools (black, isort, ruff)

[juliusz-t]

The tools allows to automatically detect (and fix) errors and style issues, so I suggest adding:

• black for consistent code formatting,
• isort for standardized import sorting,
• ruff for linting (error checking, style enforcement, etc.).

This will improve the consistency and readability of code.

Tasks:

1. Add black, isort, and ruff as development dependencies.
2. Configure them via pyproject.toml.
3. Describe usage in README.
4. Integrate checks into the CI pipeline.

[juliusz-t]

I've uploaded the tooling effect in #571. For now it's just black and isort.
I'm currently working on satisfying all the warnings from ruff, but it will need more intrusive refactoring.

[juliusz-t]

In #569 a merge roadmap is proposed in terms of code quality (type hints and test coverage) and asyncio support. I will be happy to help you complete these two tasks. Could you evaluate the idea of ​​adding these tools in context of existing Pull Requests?

[acolomb]

Please refrain from big "this fixes it all and refactors many things at the same time" pull requests. They are almost impossible to review and give little benefit for the time invested.

As with typing, I'm totally fine with adding the tool configuration, though we shouldn't have to specify many non-default options. Then anyone can run them locally or on the CI and send in smaller, self-contained pulls fixing individual (classes of) errors / warnings for a tool. When it's finally ready to run without errors, the linters can be configured as a mandatory check in the CI. Please be careful with functional changes / refactoring just because of some linter message. Plain reformatting usually has the lowest benefit / cost ratio when it comes to review time, and I do think thorough reviews are good practice for a stable library.

Hope you're okay with that approach, as I think it's the only way to get some serious review during the process.

As for current development practice, I'm using mainly flake8 and have already pushed some smaller tidying up steps last year based on that.