dsh-changelog: Automatically Generate Release Notes

`dsh-changelog` is a DSH plugin that generates release notes based on Git history. It supports automatic drafting, previewing unreleased changes, and customizing writing style. Its core features include generating release copy from PRs and commit messages, automatically filtering sensitive information, and maintaining an audit log. The plugin must be installed from a GitHub source, uses the `/unreleased` and `/release-notes` commands to manage release notes, and its output files follow the `.dsh/` directory convention.