Write documentation on how to verify a release

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
When we hold a vote on releasing Ballista, we need voters to know how to verify a release. There is a simple script that will simply run `cargo test` and check signatures, but that isn't sufficient for a distributed platform such as Ballista.

**Describe the solution you'd like**
Write documentation on how to verify a release. This should at least involve spinning up a cluster using `docker-compose` and running one query.

We do have `./dev/integration-test.sh` which seems to be broken currently (https://github.com/apache/arrow-ballista/issues/360), but we can probably fix that fairly easily.

**Describe alternatives you've considered**
None

**Additional context**
None

Start with the release-verification script described in the issue and inspect ./dev/integration-test.sh, along with the docker-compose setup. Run cargo test and check the existing signature checks, then determine what is needed to start a cluster and run one query. Done means the release documentation explains those verification steps and accounts for the integration test workflow.

Written by the indexing model from the issue text.