minimally reproducible example of devcontainer/cli#904

#904

1. git clone this repo, open in vscode with dev containers extension installed (v0.384.0)
2. build the original_container
3. copy the resulting image hash
4. fill that in the .devcontainer/compose_container/docker-compose.yml file under image
5. reopen in container, select compose_container
6. get the following error:

services.devcontainerissues.environment.[2]: unexpected type map[string]interface {}