Django-dsfr

Added management for form fields and a sample form

**Full Changelog**: https://github.com/entrepreneur-interet-general/django-dsfr/compare/v0.7.4...v0.8.0

Fix back some diverging recommandations between w3c checker and audit

Updated sidemenu to add a heading_tag parameter

Fix errors/warnings reported by the a11y audit and https://validator.w3.org

**Full Changelog**: https://github.com/entrepreneur-interet-general/django-dsfr/compare/v0.7.0...v0.7.1

What's Changed
* Dsfr 1 4 by Ash-Crow in https://github.com/entrepreneur-interet-general/django-dsfr/pull/12


**Full Changelog**: https://github.com/entrepreneur-interet-general/django-dsfr/compare/v0.6.2...v0.7.0