Support Multi-arch build on images

With the increase of ARM-based computers (edge computing, m1) a solution for multi-arch build should be proposed.

We have been able to compile the KC project by our selves, but it forces to trigger an additional step on the build process for the dev environment. From our point of view, and to avoid the publishing and use of non-official repos, the Keycloak community should include a multiarch-setup on the image publishing.

I think it will be more and more important in the close future and it eases the development in all stages