Add support for ddev/ddev-drupal-contrib

Problem/Motivation

DDEV and ddev/ddev-drupal-contrib appear to be the de-facto local development setup for contrib modules these days. It was easy to set up locally. Per the suggestion in the docs, I'd like to commit the .ddev folder to make it even easier for the next person.

See https://github.com/ddev/ddev-drupal-contrib