Switch CSS compiling for the Behat UI module from SASS to PostCSS to follow with work by Drupal core team on Claro and the Gin contrib theme team

Problem/Motivation

• Currently, custom styling compiling is done by Dart-Sass to compile SCSS to CSS files
• The drupal core team is using the postCSS method to compile dynamic styles for all core themes and modules

Proposed resolution

Switch CSS compiling for the Behat UI module from SASS to PostCSS to follow with work by Drupal core team on Claro and the Gin contrib admin theme team

Remaining tasks

• ✅ File an issue
• ➖ Addition/Change/Update/Fix
• ➖ Merge request, Patch, or Commit
• ➖ Testing to ensure no regression
• ➖ Automated unit testing coverage
• ➖ Automated functional testing coverage
• ➖ UX/UI designer responsibilities
• ➖ Readability
• ➖ Accessibility
• ➖ Performance
• ➖ Security
• ➖ Documentation
• ➖ Code review by maintainers
• ➖ Full testing and approval
• ➖ Credit contributors
• ➖ Review with the product owner
• ➖ Release notes snippet
• ❌ Release

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• N/A