Thanks for the update. The broken link is a temporary outage (caused and to be cleaned up by yours truly), URLs should stay valid indefinitely.
The relevant bit is currently in the documentation on the string data type: Data Types - Nix Reference Manual
It’s not a good place, and I simply didn’t get around to moving it yet. PRs very much appreciated. If you don’t know where to start, I uploaded a video tutorial for the first steps: https://m.youtube.com/watch?v=8ogaUFuAkCY