Add Drupal environment

[bap14]

The nginx container already contains the Drupal configuration, but Warden command doesn't have an environment. #646 adds the missing environment for Drupal.

[navarr]

Tracking progress on this here: https://github.com/orgs/wardenenv/projects/1?pane=issue&itemId=26226915

Next steps:

• I need to QA your PR and merge
• Documentation should be written on how to setup