feat: prepare ground for config directory changes

config

@@ -4,6 +4,7 @@ export REDIS_IMAGE_VERSION=${REDIS_IMAGE_VERSION:="3.2.8"}
 export REDIS_ROOT=${REDIS_ROOT:="/var/lib/dokku/services/redis"}
 
 export PLUGIN_COMMAND_PREFIX="redis"
+export PLUGIN_CONFIG_ROOT="${DOKKU_LIB_ROOT}/config/${PLUGIN_COMMAND_PREFIX}"
 export PLUGIN_DATA_ROOT=$REDIS_ROOT
 export PLUGIN_DATASTORE_PORTS=(6379)
 export PLUGIN_DATASTORE_WAIT_PORT=6379