Document the generic printer and how to write a backend

[W95Psp]

We should write a step-by-step tutorial about writting a backend for a simple language.

[franziskuskiefer]

There's a draft from @jschneider-bensch hacspec/book#14

[github-actions]

This issue has been marked as stale due to a lack of activity for 60 days. If you believe this issue is still relevant, please provide an update or comment to keep it open. Otherwise, it will be closed in 7 days.

[W95Psp]

Let's close, #533 is going to replace the generic printer, hopefully with some documentation.