Add optional DDEV development environment

Based on https://github.com/ddev/ddev-drupal-contrib. Adds a memcached service

.ddev/addon-metadata/ddev-drupal-contrib/manifest.yaml

+name: ddev-drupal-contrib
+repository: ddev/ddev-drupal-contrib
+version: 1.0.0-rc12
+install_date: "2023-10-30T15:46:18-04:00"
+project_files:
+    - commands
+    - config.contrib.yaml
+global_files: []
+removal_actions: []