fix config

docker-compose.yml

@@ -68,6 +68,7 @@ services:
       # - sqlite:///data/sqlite.db (NOT RECOMMENDED)
       # - For details see the official sequelize docs: http://docs.sequelizejs.com/en/v3/
       - CMD_DB_URL=postgres://hedgedoc:password@database:5432/hedgedoc
+      - CMD_ALLOW_FREEURL=true
       # **DOMAIN** is the domain under which HedgeDoc will be available. Just the (sub)domain, no protocol or paths.
       # You MUST change this if your instance should be available under another domain than "localhost", otherwise your
       # instance may be broken.