This PR should be merged after the new website is deployed. - [x] Rename files - [x] Add front matter section to all `.md` files in the book (necessary for Zola) - [x] Change all internal links to use Zola's linking system that checks broken links - [x] Some updates to documentation contents and organization Co-authored-by: Alex Auvolat <alex@adnab.me> Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/213 Co-authored-by: Alex <alex@adnab.me> Co-committed-by: Alex <alex@adnab.me>