Pulp

As part of #5580, we talked about logging plugin api changes in the changelog separately so it would be easy for plugin writers to identify changes in each pulpcore release.

Solution¶

1. Add new towncrier types for the plugin api: pluginbugfix, pluginfeature, pluginremoval, and plugindoc
2. Create a section of each release for these pulpcore plugin changes
3. Make sure these changes don't appear for pulpcore
4. Add docs that show ALL changelog types (not just the plugin ones)

Question: do we need a misc type for the plugin api?