Ruff linting

[maarten-ic]

Enable additional ruff linting rules

Most changes are trivial, but please check if you agree with my solution for the base ymmsl.document.Document class:

• Rules triggered by ruff:
  1. B024 Document is an abstract base class, but it has no abstract methods or properties
  2. B027 Document.__init__ is an empty method in an abstract base class, but has no abstract decorator
• I tried making __init__ an abstract method (and add a concrete __init__ method to ymmsl.v0_1.document.Document) but then mypy complains: ymmsl/io.py:34: error: Only concrete class can be given where "type[Document]" is expected [type-abstract]
  So instead I completely removed the ABC superclass from document.Document.

Suggested to review commit-by-commit and don't spend too much time at the import sorting commit 🙂