Launch additional services in separate container

The additional services (like Postgres or RabbitMQ) should be started as additional Docker services. This could for example be achieved via docker-compose.

AiiDAlab-launch would likely need some major revision to then support this, since it currently uses docker directly to manage the container(s).

## Sub-tasks:

- [x] Create proof-of-concept docker-compose file that demonstrates the approach
- [ ] Evaluate how we want to manage multiple containers within the context of aiidalab-launch (docker-compose, manually, external tool ?)
- [ ] Revise aiidalab-launch to manage multiple containers based on approach identified in previous step

## Dependencies

- [ ] https://github.com/aiidalab/aiidalab-docker-stack/pull/254