Release Kani with GH packages.

[YoshikiTakashima]

Requested feature: Release Kani Docker images with github packages.
Use case: Smoother integration to customer CI.
Link to relevant documentation (Rust reference, Nomicon, RFC):

• https://docs.github.com/en/actions/publishing-packages/publishing-docker-images

Test case:

docker pull  ghcr.io/model-checking/kani:latest

@tedinski: moving the discussion here. I think this would be the best
way to release, but open to other plans. I can own this if this plan
sounds good to you.

[YoshikiTakashima]

Potential customer running proptest (https://github.com/tokio-rs/prost.git) suggested this will make integration easier for them.

Adding under "Integration with existing testing frameworks (e.g. Proptest, Bolero)"