Move away from local installed Crystal and use `hydrofoil-crystal`
container image as runtime environment.
The included `docker-compose.yml` and `Procfile.dev` files setups everything
that is needed to automatically run the project's specs.
To start watching for changes, in a console:
$ docker compose up
(Use `docker-compose` if you're still using old version of Docker Compose)
You can press `Ctrl+C` to stop it or from another console:
$ docker compose stop
[skip ci]
Luis Lavena