ToDo:

• update system settings (at least languages)
• set Language on root document (Navigation & Properties)
• create site properties
  • navMainRoot
  • navQuicklinksRoot
• create footer
  • create /{language}/snippets/footer with Controller App\Controller\Snippet\FooterController::footerAction
• create /{language}/quicklinks
• delete this todo in /templates/default/default.html.twig