Make it clear the getting started example isn't production ready

[rijkvanzanten]

The brief Docker Compose example here uses SQLite as the database. While good for a quick local test, this isn't a recommended setup for full production usage. We should add a callout with a link to a full production docker compose example to clarify this. Ref https://community.directus.io/t/are-postgres-and-redis-not-recommended-for-use-with-directus-anymore/1268/2