Add one new book and update one existing

Add one new book and update one existing

Update "POSTGRES: The First Experience" to the current edition
of the book,  and update the cover image (removing the old one
in the process.  This also adds "PostgreSQL 14 Internals" as a
new book.

Submitted-by: Pavel Luzanov <p.luzanov@postgrespro.ru>
Discussion: https://postgr.es/m/4dc340fa-712b-9158-019a-cccbd830535c@postgrespro.ru