Add s390x arch docker image

[rohitsakala]

S390x PR traefik/traefik#8729 is merged in Traefik

For Docker library images script to publish s390x docker image, this PR is necessary.

Fix #20

[ldez]

https://github.com/docker-library/official-images/#architectures-other-than-amd64

[rohitsakala]

https://github.com/docker-library/official-images/#architectures-other-than-amd64

Hello @ldez , what I understood is that when Traefik releases a new version in Feb last week which will have support for s390x, the https://github.com/docker-library/official-images repo will be updated with new version and will add s390x to this line https://github.com/docker-library/official-images/blob/master/library/traefik#L11, then docker library scripts will run this Dockerfile https://github.com/traefik/traefik-library-image/blob/master/alpine/Dockerfile for all architectures. So, I made this PR.

Let me know if my understanding is wrong. Thanks :)

[rohitsakala]

Hi @ldez , any reviews on this ? Thanks

[rohitsakala]

@ldez , docker still outputs s390x images in Jenkins - https://doi-janky.infosiftr.net/job/multiarch/job/s390x/

[ldez]

We will manage the Docker part.

[rohitsakala]

Thanks @ldez . Please add s390x arch too in here https://github.com/docker-library/official-images/blob/master/library/traefik#L11 when upgrading traefik from v2.6.1 to v2.6.2 in here https://github.com/docker-library/official-images/blob/master/library/traefik#L10

[ldez]

We will manage the Docker part.