Adding prefix `docker.io` for image references for podman/fedora support.

[DMantis]

I suggest adding docker.io/ prefixes for compose.yml image definitions, so redhat-based distros with podman deployments work without asking the source of the image.

Otherwise it asks for the source interactively, which gets ansible deployments stuck on this menu:

If I assume correctly, the image is supposed to be served from dockerhub, so simply adding docker.io/ prefix to all images would make the instructions base distro and container runtime agnostic.