[FEAT] Provide a theme based on french design system

[micedre]

We should provide a basic theme based on https://www.systeme-de-design.gouv.fr/ .
Either by reimplementing the login theme or using https://github.com/dataesr/react-dsfr and https://github.com/InseeFrLab/keycloakify