fix: add production configuration file and update docker-compose to remove unnecessary environment variables

docker-compose.yml

@@ -26,14 +26,7 @@ services:
       - ${PA11Y_PORT:-4000}:4000
     environment:
       NODE_ENV: ${NODE_ENV:-production}
-      PORT: 4000
-      NOINDEX: ${NOINDEX:-true}
-      READONLY: ${READONLY:-false}
-      SITE_MESSAGE: ${SITE_MESSAGE:-}
       WEBSERVICE_DATABASE: mongodb://mongodb:27017/pa11y-webservice
-      WEBSERVICE_HOST: 0.0.0.0
-      WEBSERVICE_PORT: 3000
-      WEBSERVICE_CRON: ${WEBSERVICE_CRON:-0 2 * * *}
     networks:
       - pa11y-network