automatize CD of docker image with kiwi and obs

discussed with @alvarocarvajald @ricardobranco777

# desc:

When an user push a change to the dockerimage file, this should be rebuilded and then delivered to various registries.

# technical details:

implement github action on branch so that when PR got merged, this trigger obs to build image and other CD.

https://en.opensuse.org/Building_derived_containers