[Feature Request] Read devcontainer.json from a docker volume

I'm always cloning repositories into named docker volumes, since mounting workspaces folders into docker machines introduces performance impacts, and for keeping my host clean. This is done via the `Clone Repository in Named Container Volume`-option provided by your remote containers extension.

It would be pretty cool if I could do the same using the CLI, for building, starting and running commands, like `devcontainer up @myproject` or similar.