Automatically insert the code snippets into the K8s tutorial

[tonyandrewmeyer]

Now that we have the K8s tutorial in git, we should be able to have a helper script that takes the relevant code snippets from the tutorial repository and inserts them into the doc files (or some other technique that means that the docs are composed rather than hand-coded). This would ensure that they remain in sync and that the code is tested and formatted consistently (once each chapter has tests for all features, and CI is set up).

Maybe the script could even take care of stitching the chapters together? There's a "previous" and a "next" link in each chapter, as well as instructions at the start for how to check out the previous branch and create a new one, and instructions at the end for how to compare the branches.