Configure ruff formatter in CI

[danielhollas]

This PR proposes to use a ruff formatter for the code and enforce it in the CI.
Docs for ruff formatter
setup in PyCharm
One advantage of ruff is that it is also a linter (although I am not setting up the linter here, am planning to discuss separately in a follow-up PR), so we would have a single tool for both.

Ruff uses a formatting style of another very common formatter called "black", and is quite different from what we have now. @JanosJiri if you have a strong preference for the current format, that is totally fine, but in that case you need to figure out which formater PyCharm uses in your setup so I can use it as well and we can enforce it in CI.

Besides the choice of the formatter, there are other things to be decided:

• line length: Right now I have configured maximum line length to 130 to preserve existing format. I would personally preferred a bit shorter lines, but it is entirely up to you. @JanosJiri perhaps you can experiment locally with configuring shorter lines and see what looks best to you.
• Do we use single or double quotes? The current code was inconsistent so I used ruff's default of double quotes, but I have no strong opinions on this, both are fine and it is configurable.

[JanosJiri]

@danielhollas is this ready for review or do you still plan to work on it? I see you requested a review but then you changed it back to draft.

[danielhollas]

Oh yes, this is ready, (although obviously this will need to be rebased on top of main). Not sure why I changed this to draft, the main tasks are now for you to decide if the change in format is okay etc as outlined in the PR message.

[danielhollas]

I guess I changed it to draft since there are a bunch of decisions that need to be made before merging.

[JanosJiri]

I'm fine with this formatting. I like a bit longer lines around 130 characters, if you are ok with that. The only other changes I noticed are using double quotes, which is fine, and having spaces around arithmetic operators, which I don't like that much visually but I found ruff can't change that, so lets keep it like that. I don't want to change my PyCharm formatting as I spent quite a long time setting it up but I can always use ruff before committing, that's not an issue. Thus, I think we can go with that.

[danielhollas]

Out of curiosity what formatter do you use in PyCharmm?

[JanosJiri]

Pycharm has its own formatting tool where you can configure even tiny details. It's very convenient, see https://www.jetbrains.com/help/pycharm/reformat-and-rearrange-code.html if interested.

[danielhollas]

I'll close this for now, I created issue #55 in case we want to do this in the future.