Make Stable Base Theme Compatible for Drupal 10

[kevinreiss]

Our pinwheel custom theme depends on the "stable" base theme. There are three options for keeping this D10 compatible.

https://www.drupal.org/node/3309392

Option 1 introduces a contrib dependency that should work without any changes on our part. Option 2 should "likely" work but may require us to make some changes to the pinwheel custom theme. Option 3 seems too much work. Given the legacy nature of the project maybe we should pursue option 1. It is my expectation that we will move this site to OIT hosting in 2024 (hopefully by mid-year).

• [ ] Install contrib base theme locally: https://www.drupal.org/project/stable; test theme
• [ ] Deploy to staging, test theme
• [ ] Deploy to production

[kevinreiss]

See https://github.com/pulibrary/researchdata/pull/253 for a similar action for a different theme on researchdata.