Add the documentation about the example of using virtio-blk driver
to pass the zoned block devices through to the guest.

Signed-off-by: Sam Li <faithilikerun@gmail.com>
Message-id: 20230508051916.178322-5-faithilikerun@gmail.com
[Fix pre-formatted code syntax
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>