Add support for ORCID IDs in the contributor collections

[JamesEnglish1028]

For research communities, the ORCID ID is persistent identifier used to distinguish researchers, authors, contributors from one another especially when they have the same name.

the format in URI form is is https://orcid.org/xxxx-xxxx-xxxx-xxxx.

For Example James English would be

The expression could be

{
"author": {
   "name": "James English",
   "identifier": "https://orchid.org/0000-0003-1899-7091"
   }
}

[HadrienGardeur]

URIs are already supported as our default way of dealing with extensibility for identifiers, but I agree that we could put a little more focus on ORCID.

In addition to supporting URI schemes, we could list URI templates as well: https://readium.org/webpub-manifest/contexts/default/#identifier