vcard:AddressBook

Hi all,

In the Solid CG we are using `vcard:AddressBook`, but it came to our
attention that this class is not defined in https://www.w3.org/TR/vcard-rdf/
.

The document says:
> If you wish to make comments regarding this document, please send them to
semantic-web@w3.org>

We have documented/used `vcard:AddressBook` in the following places:
* https://pdsinterop.org/conventions/addressbook/
*
https://github.com/SolidOS/contacts-pane/blob/ae1819676bb19a2b0cc7a02b4417c96751ff5297/mintNewAddressBook.js#L60-L75
*
https://github.com/solid-contrib/data-modules/blob/d732671f5c5a37b9748ce90bf3220e2e36336d8f/contacts/src/rdflib/ContactsModuleRdfLib.ts#L48

How can we go about adding `vcard:AddressBook` to the vCard ontology, or
what would be the best way forward here?


Many thanks,
Michiel de Jong
Co-chair
Solid CG