Add DockerHub image manifest list for Windows and Linux registry:2 images

[micahyoung]

• Create manifest list at cnb/registry:2
• Should refer to lasest images for;
  • index.docker.io/library/registry:2@sha256:
  • index.docker.io/stefanscherer/registry-windows:2.6.2-1809@sha256:

Syntax Ex:

docker manifest create micahyoung/registry-test5 \
  registry@sha256:c2748bc237015d14ef65355f03b77f0a7f0566d440f447e670f3333906f0f5da \
  stefanscherer/registry-windows@sha256:631b26ce1bc3d8ff9b2d4522bd4a1c1a9a2bacdc140e78b0c16bc343343684d0
docker push micahyoung/registry-test5

[dfreilich]

@micahyoung Is this still something we should do?