Simplify and update homepage

[clemsos]

There is several thing that needs to be done to make this homepage clean. Since the book is not there, it needs to be simplified to become a single-page website.

• [x] remove the menu ?
• [x] merge table of contents and intro/description (at the bottom)
• [x] HOWTO participate
• [x] ref to audiobook
• [x] link to press kit + contact
• [x] add posts
• [x] publish reviews

Almost all this already has an issue here : https://github.com/costoffreedom/costoffreedom.cc/issues?q=is%3Aopen+is%3Aissue+label%3Ahomepage

[clemsos]

started to address in a2676758a89f255a30e19b5564b4ee7005565e43

[clemsos]

ok seems that the homepage looks better now