update installation readme
update installation readme

Signed-off-by: Antonio Murdaca <f9809039ea4850e75dcb8d80b778844aa463358f@redhat.com>

containers/image,jwhonce/skopeo,mtrmac/skopeo,projectatomic/skopeo,mathewkoshy493/manifest-tool,projectatomic/skopeo,runcom/skopeo,masters-of-cats/image,estesp/manifest-tool,mtrmac/skopeo,runcom/skopeo,mikebrow/skopeo,mtrmac/skopeo,mikebrow/skopeo,estesp/manifest-tool,mathewkoshy493/manifest-tool,jwhonce/skopeo,containers/image