Added env var to docker-compose to enable config mutations by default

docker-compose.yml

@@ -5,6 +5,7 @@ services:
             ALLOW_CONFIG_MUTATIONS: 'true'
             ytdl_mongodb_connection_string: 'mongodb://ytdl-mongo-db:27018'
             ytdl_use_local_db: 'false'
+            write_ytdl_config: 'true'
         restart: always
         volumes:
             - ./appdata:/app/appdata