add citation and zenodo badge

[nden]

Adds a Zenodo DOI and a citation file based on the current contributors list

Checklist for maintainers

• [ ] added entry in CHANGES.rst within the relevant release section
• [ ] updated or added relevant tests
• [ ] 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
• [ ] Make sure the JIRA ticket is resolved properly

[codecov[bot]]

Codecov Report

Merging #6978 (1d93cd0) into master (abd9b56) will decrease coverage by 0.44%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6978      +/-   ##
==========================================
- Coverage   79.27%   78.82%   -0.45%     
==========================================
  Files         414      414              
  Lines       37459    37781     +322     
==========================================
+ Hits        29695    29781      +86     
- Misses       7764     8000     +236     

Flag	Coverage Δ		*Carryforward flag
nightly	79.24% <ø> (ø)		Carriedforward from f6ca05e
unit	53.11% <ø> (-0.01%)	:arrow_down:

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
jwst/cube_build/ifu_cube.py	79.63% <0.00%> (-12.04%)	:arrow_down:
jwst/tweakreg/tweakreg_step.py	65.54% <0.00%> (+2.77%)	:arrow_up:

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[zacharyburnett]

Does this warrant a changelog entry so users are aware of the new citation?

[jdavies-st]

FWIW, I updated the release procedures WIKI here so that the CITATION.cff file is updated to the current release version and release date. ✅