Add ruff as a linter with basic rules

[maclick]

Created ruff configuration that uses these rules:

• pycodestyle
• pyflakes
• isort

Also created github workflow for running ruff, as this is really light workflow, I've configured it to run on every push

[metenn]

I don't know why nobody has commented on this yet, I think Ruff is a great step forward!
I can see Ruff was used to format the codebase within this PR already. Maybe it'd be better if the pass was done in a separate PR, or in a single, final commit, so this PR could be rebase-merged to keep future uses of git-blame more manageable?