Allow sections to only include issues or pull requests

[steven-sheehy]

Problem

I target both issues and PRs to milestones, but I'd like to only include issues in the changelog. Having both in the changelog duplicates information and makes it harder to read. For Dependabot, there is no corresponding issue so I'd like to include both or just PRs for the dependencies section.

Solution

• Add a changelog.sections[].type enum property with values ANY, ISSUE, or PULL_REQUEST
• Default type property to ANY if not specified for backwards compatibility with existing configuration
• Filter sections based upon property to only contain the requested issue type

[wilkinsona]

Having both in the changelog duplicates information and makes it harder to read.

We avoid this problem by only having an issue or a pull request in a milestone for a particular change. In the spirit of that, I'll close this as superseded by #86.