[bug#58463] [PATCH] * doc: guix-cookbook: Add a "Guix API usage examples"

[Fulbert]

Hello,

Attached I propose a patch with an additional chapter to the
guix-cookbook. It is a transcript of Simon Tournier examples used in
his "Guix REPL - to infinity and beyond" presentation at the
10 years of Guix event.

I made the resulting html available at the following address, so
the interested parties can quickly preview it.

https://fulbert.neocities.org/guix/10-years-of-guix/simon-tournier-guix-repl/guix-cookbook/index.html

Best regards,
Fulbert