overhaul FAQ

[orangecms]

outdated ref to Horizon, phrasing in thr future that has long passed ...

https://github.com/linuxboot/linuxboot.org/blob/main/content/page/faq.md?plain=1

Do we want to drop the FAQ in favor of a single front page and move the references to the book?

[orangecms]

This 0abac45
was based on https://news.ycombinator.com/item?id=16259373

I have read through almost the whole thread and filed corresponding issues for the book.