Add pre-commit workflow including ruff

[schuenke]

closes #197

Probably nobody wants to review all changes manually, but maybe you can checkout this PR and just check that your last ~10 pypulseq sequences and/or related projects still work fine @FrankZijlstra @btasdelen and maybe even @mavel101 @wtclarke

IMO, this is a necessary step towards a better maintainable package and it will simplify to proceed with #95 and #123

Some infos about pre-commit:

• I added pre-commit as an optional "test" dependency in pyproject.toml
• I added a pre-commit GitHub workflow that runs in every PR (and it has to pass to be able to merge the PR)
• you can download pre-commit from PyPi using pip install pre-commit
• after downloading, it can be installed using the pre-commit install command
• when installed, it will run locally every time BEFORE you create a commit. This way you directly know if it will pass the GitHub workflow
• if you still want to commit something that does NOT pass all pre-commit hooks, you can skip the pre-commit checks using git commit -m "your msg" --no-verify. Note that this does NOT skip the pre-commit GitHub workflow.
• additional hooks I would like to add in the future: mypy, check-docstring-first

Some further infos about RUFF:

• RUFF is "an extremely fast Python linter and code formatter"
• it is used in many large projects like FastAPI, scipy, pandas, ...
• it supports over 800 different rules
• it supports a hierarchical configuration (different configs for subfoldes like tests or seq_examples)
• editor integrations for VsCode and my other editors are available (I highly recommend it!)
• I already added some additional rules that I would like to enforce in the future. These are commented out in RUFF section of the pyproject.toml file.

[btasdelen]

Looks good. I tested with a couple sequence, did not see any issues.

[schuenke]

I also added the config for pre-commi ci now. This allows automated fixes in PRs and will check monthly for updates of the different pre-commit hooks that we use. If we want to activate it, @sravan953 hast to login at https://pre-commit.ci/ and add an installation for pypulseq (just select the repo - thats all).

11ad246 is a good example that pre-commit.ci would have fixed automatically 👆

[schuenke]

@FrankZijlstra are you fine with merging it? Or you wanna have some extra time to review it as well?

[FrankZijlstra]

I had a quick look and though I'm not familiar with RUFF and how to set it up, from looking at the style changes in the files I think it looks good. Maybe it would be a good idea to add a note to the readme about how to set up pre-commit (basically what you put here)?

I haven't tested it with my sequences, but looking at the changes I don't see anything that would break. So I'm fine with committing this now.

If I remember correctly I still have a branch where I added all the sequence examples to the test_sequence unit tests. And then it shouldn't be too hard to put the new tests in a PR soon(ish), and we can check a bit more elaborate set of sequences automatically.