Align the docker image tag name in the compose.yml with the build CI/CD

Addressing Issue #2 (closed) the docker compose.yml file currently expects an image tagged "zarr-to-opendap" to exist, which is what it then runs. That said, looking at the CI/CD YAML @ewojtylko1 wrote, docker build is called using a dynamic tag from Gitlab secrets (I'm assuming...is this correct?).

I just wanted to flag this issue such that whatever tag you end up using can also be present in the compose file. GitLab secrets do not appear directly compatible with docker-compose w/o an intermediate step of writing to a txt file or something - see https://docs.docker.com/compose/use-secrets/. For now, I am committing the compose file I have, which is tested and works (given you use docker build . -t zarr-to-opendap)

Also pinging @ptomasula_limno.com