Support for ephemeral ports in compose

[bforbis]

Try running a compose where ports for a service are bound to an ephemeral port, as documented in https://docs.docker.com/compose/compose-file/compose-file-v3/#ports

version: '3'
services:
  foo:
    build: .
    ports:
      - 3000

When starting this using nerdctl compose up, I receive an error:

FATA[0000] unsupported port number: 0