✨ Feature: "(Get) The Book" should be a dropdown menu

[JoshuaKGoldberg]

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• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my request.
• This is the appropriate issue form for the tooling issue I would like to report.

Expected

Learners can acquire the book on at least O'Reilly and Amazon. It'd be nice if the book link was a little dropdown that surfaced those >=2 links.

Actual

It's just a normal link to O'Reilly now.

Additional Info

No response