Clarify changelog entries (or add a new "Feature Improvement")

Description

When submitting a change that improves a feature but without changing its behavior it's hard to choose which changelog entry type suits best.

Please specify the index for the category of your change:

1. New feature
2. Bug fix
3. Feature change
4. New deprecation
5. Feature removal
6. Security fix
7. Performance improvement
8. Other

3. Feature change seems ambiguous has it could mean that the feature behavior has changed.

Proposal

• clarify 3. Feature change so that it's only about feature behavior change: 3. Feature behavior change
• add a new choice: 9. Feature improvement