Credit generator: backport proofreading of the bookpublishing project and make it translatable.
The new credit generator introduced many new lang strings; but hardcoded.
https://www.peppercarrot.com/en/static6/sources&page=credits
Before merging them into language keys; it's also would be better to backport the proofreading and formating adopted at final by the book project. The txt data can be found here: https://framagit.org/peppercarrot/book-publishing/-/tree/master/txt