Depot CI now supports case expression in GitHub Actions workflow syntax

Depot CI now supports the case expression in GitHub workflow syntax, matching the latest GitHub Actions expression functions. This allows you to map values to different outputs without chaining multiple if conditions:

steps:
  - run: echo ${{ case(github.event_name == 'push', 'Pushed', github.event_name == 'pull_request', 'PR', 'Unknown') }}