Support RDF-Star requests and responses

[bergos]

The serializer and parser to send and receive RDF data should support RDF-Star data. The package relies on the parser of N3.js, which already has RDF-Star support. @rdfjs/to-ntriples takes care of serializing the triples. That package may need an update.

• RDF-Star data can be serialized
• RDF-Star data can be parsed

See also:

• RDF Star Support #43