[ELPA] New package: isbn.el

Hi everyone,

*This package was not written with AI.*

I would like to request the inclusion of a new package to GNU ELPA:
isbn.el.  You can find the repo here: <https://git.sr.ht/~cook/isbn.el>.

isbn.el is a small library to validate, convert and hyphenate ISBNs both
programmatically and interactively.  The Commentary section of 'isbn.el'
explains the entire library.

Having signed all the paperwork with the FSF, I would prefer that the
package go to GNU ELPA, but I'm fine if Non-GNU ELPA is deemed a better
fit.

Also, I would definitely consider myself an amateur lisper, so I would
appreciate any feedback!

-- 
Maximilian Cook