x/website: add featured international books

[fgm]

What version of Go are you using (go version)?

(irrelevant)

Does this issue reproduce with the latest release?

(irrelevant)

What operating system and processor architecture are you using (go env)?

(irrelevant)

What did you do?

• Browse the discovery site, looking for recommended books.
• Find the "Featured books" on the home page. Click the link to https://go.dev/learn/#featured-books
• Ask about it on go-nuts.
• @ianlancetaylor suggested I open an issue here and send a pull request.

What did you expect to see?

• A short list of english books (like the one I found)
• A short list of one book per major language

What did you see instead?

• Five books, all of them in english
• No book in other languages, not even a link to https://github.com/golang/go/wiki/Books

[ianlancetaylor]

CC @stevetraut

[gopherbot]

Change https://golang.org/cl/337969 mentions this issue: x/website: add featured international books.