Tweak book covers

[sapegin]

• Use SVG covers
• Move covers and headings to React
• Fix extra whitespace before book descriptions because of floating covers
• Remove anchors from headings on landings
• FIx wide columns on small screens
• Add titles to books in the footer
• Tweak heading sizes a bit

SVG covers looks good:

[bebraw]

Yup, very good. 👍

[sapegin]

They are also more than two times smaller ;-)