Add enhancements section to the changelog

[maxrjones]

Description of proposed changes

Some of the enhancements between releases would be helpful for users to know about (e.g., #5819, #5924). This adds an enhancement section to the release drafter configuration for PRs with an 'add-changelog' and 'enhancement' tag.

Fixes #

Reminders

• Make sure that your code follows our style. Use the other functions/files as a basis.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.