ContextSet Doc Clarification

[DanKaplanSES]

I think A few points about the ContextSet: implies that the topic is changing, so hopefully my edit will override that potential assumption.

Motivation and Context

I was confused reading the documentation and I think this could prevent confusion in the future

Types of changes

• [x] Docs change / refactoring / dependency upgrade
• [ ] Bug fix (non-breaking change which fixes an issue or bug)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Renamed existing command phrases (we discourage this without a strong rationale).

Checklist

• [x ] I have read the CONTRIBUTING document.
• [ ] My code follows the code style of this project.
• [ ] I have checked that my code does not duplicate functionality elsewhere in Caster.
• [ ] I have checked for and utilized existing command phrases from within Caster (delete if not applicable).
• [ ] My code implements all the features I wish to merge in this pull request.
• [ ] My change requires a change to the documentation.
• [x ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests pass.

Maintainer/Reviewer Checklist

• [ ] Basic functionality has been tested and works as claimed.
• [ ] New documentation is clear and complete.
• [x] Code is clear and readable.