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)

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• 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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.38%. Comparing base (aeb7469) to head (f860547).

Additional details and impacted files

@@            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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[melanieclarke]

Sounds like a good idea to me! Thanks for fixing all the formatting errors as well.