add a flag for relative root

having removed the `-i` image reference, now relying on using skopeo independently to pull, then bsi to unpack, we need an way to run the collection scripts against a particular root path

Start by locating the collection scripts and the command-line argument handling in this Shell project. Determine how a relative root path should be supplied, then verify that running the collection scripts with the new flag targets that path instead of the default root.

Scritto dal modello di indicizzazione a partire dal testo della issue.