Run quickstart script as a test

In order to verify that [the quickstart guide](https://github.com/firecracker-microvm/firecracker-containerd/blob/master/docs/quickstart.md) works as expected, we should run the script as an e2e test in the CI system. This will likely require figuring out a way of parsing the script out of the markdown and/or having the markdown just reference a standalone script.