Add changelog to docs

[braingram]

This PR adds the changelog to the sphinx documentation.

https://jwst-pipeline--8716.org.readthedocs.build/en/8716/jwst/changes.html

Adding the file to sphinx revealed many formatting issues in CHANGES.rst fixed in this PR.

Checklist for PR authors (skip items if you don't have permissions or they are not applicable)

• [x] added entry in CHANGES.rst within the relevant release section
• [ ] updated or added relevant tests
• [x] updated relevant documentation
• [ ] added relevant milestone
• [x] added relevant label(s)
• [ ] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR
• [ ] All comments are resolved
• [ ] Make sure the JIRA ticket is resolved properly

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 60.38%. Comparing base (aeb7469) to head (f860547). Report is 18 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8716 +/- ## ========================================== + Coverage 60.36% 60.38% +0.01% ========================================== Files 372 372 Lines 38338 38337 -1 ========================================== + Hits 23142 23148 +6 + Misses 15196 15189 -7 ```

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