Add testing for prod docker

[stefandeml]

In release.sh after building the docker some examples should be tested before the container gets pushed

[stefandeml]

this could be a good command to start with:

docker run zokrates /bin/bash -c "find examples/TestStdlib/hashes -name \"*.code\" | xargs -n 1 -I % sh -c 'echo %; ./zokrates compile -i % --light || exit 255; ./zokrates compute-witness || exit 255'"