✨ Add nox session for checking if the changelog got updated

[tkilias]

Background

• For most PR, we need to update the changelog to inform the users what was changed
• Currently, we often rely on remembering it or a checkbox in a PR template
• This leads to forgetting sometimes

Acceptance Criteria

• Add a nox session which checks if the changelog file of the current version was updated
  • To be discussed: Do we check only check that it was updated, or do we also check if the current ticket was added?
• Try it out and decide on further progression, should we add a precommit hook and/or a Github Workflow which can be disabled with commit message trigger.