Consider adding an equivalence of EXPOSE

Per https://docs.docker.com/engine/reference/builder/#expose:

The EXPOSE instruction does not actually publish the port. It functions as a type of documentation between the person who builds the image and the person who runs the container, about which ports are intended to be published.

Some container service (like Azure App Service) consumes this metadata to automatically configure the correct port-mapping to the container. Without this metadata, users of these service will need to set this on the deployment side.

cc @jonjohnsonjr