Catégories de pages (#2440)

* wip page categories + l10ns

* page categories

* categories linked to pages

* fix subnav + tablist

* Fix "hugo_ancestors_for_special_page" for page categories

* fix staticable + git_path

* add category mode to block template pages

* clean

* fix block

* remove page quantity (unmanageable)

* wip api page categories

* API Page Categories

* exclude spec folder from codeclimate

* fix

* small fixes

* schema

* fix spec

* add category_ids to page spec

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Co-authored-by: Arnaud Levy <arnaud.levy@noesya.coop>
Co-authored-by: Arnaud Levy <contact@arnaudlevy.com>