[spotify piece] Adding possibility to pass a list of items



when getting a list of item from a playlist I would like to make only one call to the spotify api to add them to another playlist just to be sure I am not getting any rate limit error.

Would it be possible ton indicate the location of a field in a list and let the piece loop on itself to get the spotify uris ?

something like: item.infos.uri and then for each item in items, the piece would get the uri at the specified location

Happy to answer any question, or help (if a PR is necessary)