use `towncrier` to handle change log entries and update new pull request checklist

[zacharyburnett]

follow-on to https://github.com/spacetelescope/romancal/pull/1375

old checklist

Checklist

• [x] Added entry in CHANGES.rst under the corresponding subsection
• [ ] updated relevant tests
• [x] updated relevant documentation
• [ ] Passed romancal regression testing on Jenkins / PLWishMaster. Link: https://plwishmaster.stsci.edu:8081/job/RT/job/romancal/XXX/

new checklist

Tasks

• [ ] update or add relevant tests
• [x] update relevant docstrings and / or docs/ page
• [ ] Does this PR change the public API? (if not, label with no-changelog-entry-needed)
  • [x] write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • [ ] start a romancal regression test with this branch installed ("git+https://github.com/<fork>/roman_datamodels@<branch>")

news fragment change types...

- ``changes/.apichange.rst``: change to public API - ``changes/.bugfix.rst``: fixes an issue - ``changes/.general.rst``: infrastructure or miscellaneous change

[codecov[bot]]

Codecov Report

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

Project coverage is 97.68%. Comparing base (087a60d) to head (7fbf0a3). Report is 44 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #384 +/- ## ========================================== + Coverage 97.56% 97.68% +0.12% ========================================== Files 30 37 +7 Lines 2788 3370 +582 ========================================== + Hits 2720 3292 +572 - Misses 68 78 +10 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[braingram]

Looks like docs failure is due to formatting in the existing changelog: https://github.com/spacetelescope/roman_datamodels/blob/main/CHANGES.rst?plain=1#L268

Would you remove the backticks or make them double?