zenflow/composite-service

# TODO

- test
  - Simplify test utils by using `stream-line-reader` package.
    May need option to log each stream line for debugging,
    for when line isn't matched and stream continues until Jest timeout
    (not end of stream, which would give us a helpful error)

- community
    - https://github.com/zenflow/composite-service/community
    - PR to add composite-service example to https://docs.docker.com/config/containers/multi-service_container/