throw an error if image version doesn't match package version

[threepointone]

via @jahands

Could we add some kind of detection for when your Dockerfile is out of date with the version of @cloudflare/sandbox that you're using? I updated the npm package a few days ago and realized later that it's been completely broken, and the logs were not clear at all why it was broken:

and maybe stress in the Dockerfile example + docs how important it is to keep the Docker base image + npm package in sync?

[threepointone]

fixed via #133