Check and add import linter to BaseConfig

[ArBridgeman]

Summary

The import linter was originally added in #149, but unfortunately, it was not added into the PTB routine tasks or implemented within the various team projects:

• https://github.com/search?q=org%3Aexasol%20importlinter&type=code

At the time of writing this, only the PTB has this marked and setup. The transformers-extension has it marked, but it looks to not be properly set up.

It's currently marked as experimental under the nox session lint:import.

Task(s)

• Verify the usefulness in our projects
• Usually tools pick up . files related to them or use an entry in the pyproject.toml for settings. Is there a reason why we need this specified in the BaseConfig?
• Verify lint:import implementation
• Add to CI pipeline and/or pre-commit hook
• Update changelog, documentation, etc.