Add example local environment with traefik (#1091)

* Add example with traefik and keycloak

* Switch to dex

* Remove unneeded change in keycloak settings

* Taken into account review comments

* Add changelog entry

Co-authored-by: Frédéric Collonval <frederic.collonval@ariadnext.com>
Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>