Feature 292 release dropdown menu

[lisagoodrich]

Pull Request Testing

• Describe testing already performed for these changes:
  
  I've added dropdown menus to the release note section. The below files have been changed so the dropdown menus will work:
  config.py
  docs/requirements.txt file.
  METcalcpy/.github/workflows/documentation.yml

I have tested all of the dropdown menus.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  
  Please open a couple of the dropdown menus. Let me know if there are any problems or inconsistencies. All should be running smoothly. Here is the link:
  https://metcalcpy.readthedocs.io/en/feature_292_release_dropdown_menu/Users_Guide/release-notes.html

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]

• Do these changes include sufficient testing updates? [n/a]

• Will this PR result in changes to the test suite? [No]
  
  If yes, describe the new output and/or changes to the existing output:
  

• Please complete this pull request review by [4/4/23].
  Date is negotiable.

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[jprestop]

Thank you @lisagoodrich for making these changes. I have reviewed the content, both within the PR and via RTD, and everything looks good. Unfortunately, some "Python vulnerability checks" are failing. I do not know why this is, but I believe it does not have to do with your changes. I am going to reassign this PR to @bikegeek, because she will have a better idea of what the error is about and how to fix it. I defer approval to her, pending the passing of the tests.

[jprestop]

@bikegeek was able to resolve the testing failures (thank you!). I approve this pull request.