Add scriv to simplify creating/updateing the changelog

[Nicoretti]

Summary

Add scriv to simplify creating and updating the change log.
(Get rid of the unversioned "not released" log entries etc.)

Tasks

• Add scriv to dev dependencies
• Add configuration section to pyproject.toml
• Update release target accordingly, e.g. add check if change log was written and committed.
• Add templates if needed