Add config.ddev-drupal-core-dev.yaml from waiting PR

This is part of justafish#31

Rebase will be required when that goes in.

Author: rfay

install.yaml

@@ -32,7 +32,7 @@ post_install_actions:
 
 removal_actions:
   - |
-    for item in ../core/phpunit.xml ../core/.env ../.gitignore; do 
+    for item in ../core/phpunit.xml ../core/.env ../.gitignore; do
       if grep '#ddev-generated' ${item} >/dev/null; then
         rm -f ${item}
       fi