Add awareness of docker-compose

I'm not sure of all the goodies this might bring, but it might include:
* Stopping/starting whole stacks (based on docker-compose.yml)
* Viewing meta info that the docker-compose config creates (e.g. env vars passed in, links, networks, commands executed etc)
* Selection of which docker-compose file to use (some projects have more than one), to easily switch between different configurations.
* show info about images being used for each service, or otherwise the build of a project if that's the case.

etc...

The issue names no source files, tests, or entry points and lists several possible Docker Compose capabilities. Start by surveying the extension structure and existing Docker integration, then confirm one scoped capability and its acceptance criteria; done cannot be determined from the current issue alone.

Written by the indexing model from the issue text.