Update policy and implementation for changelog entries #16569
Description
What is the problem this feature will solve?
This is jumping off of the discussion in #16562. The specific question there is whether the addition of type annotations should merit a changelog entry.
The current policy is basically that only user-facing changes should be highlighted with a changelog entry. That has been interpreted so that documentation updates or adding type annotations do not get changelogs. However, "user-facing" can reasonably be interpreted more liberally as changes that enhance the user or developer experience with astropy.
I would argue that #16562 is both a substantial amount of manual effort and substantially improves the user experience using the stats package. People reading the changelog should be made aware of this.
Being more self-serving, my own #16561 documentation update was at least 16 hours work and it would give me a good feeling to see that effort showing up in the changelog.
We are always trying to find ways to reward new contributors, but if they improve the documentation then that PR goes essentially unnoticed.
Describe the desired outcome
If a contributor wants a changelog entry associated with their PR, then it is allowed. For new-ish contributors, adding a changelog would be the default instead of opt-in.
Add a documentation changelog category to recognize this important category of contributions.
Additional context
No response