Add the ability to shutdown the devcontainer

[erichlf]

Currently once a devcontainer is running it will continue to run and there is no way to remove that container. Adding this would allow a user to control resources better on their machine.

[erichlf]

This is a planned feature in devcontainer-cli, which can be seen in the https://github.com/devcontainers/cli/blob/main/README.md.

[erichlf]

Alternatively, instead of waiting for the feature to be implemented we could get the docker id like so:

docker_id=$(docker ps -q -a --filter label=devcontainer.config_file="${WORKSPACE}"/.devcontainer/devcontainer.json)

and then run

docker kill $docker_id

Of course we would want to translate this to lua.