Would be very useful to add support for Dockerfile targets for deploying apps inside of monorepos.

It is a common pattern to have a top level Dockerfile, with a target for each app: https://pnpm.io/docker#example-2-build-multiple-docker-images-in-a-monorepo

I've seen few other requests asking for this feature:
* https://station.railway.com/questions/use-dockerfile-targets-564aea7a
* https://station.railway.com/questions/how-can-i-specific-target-for-dockerfile-24307849