add CEURVOLNR, CEURURN, CEURPUBYEAR,CEURVOLTITLE to rdfA like scraping

[WolfgangFahl]

which will make the info also available in the json result e.g.

{
    "fromLine": 133,
    "toLine": 154,
    "valid": 1,
    "url": "http://ceur-ws.org/Vol-3361/",
    "acronym": "SwissText 2022",
    "title": "Proceedings of the Swiss Text Analytics Conference 2022",
    "loctime": "Lugano, Switzerland, June 8-10, 2022",
    "tdtitle": "Proceedings of the Swiss Text Analytics Conference 2022 (SwissText 2022) Lugano, Switzerland, June 8-10, 2022.",
    "volname": "Swiss Text Analytics Conference 2022",
    "editors": "Manuela Hürlimann, Roberto Mastropietro, Daniele Puccinelli, Fabio Rinaldi, Mark Cieliebak",
    "submittedBy": "Manuela Hürlimann",
    "published": "2023-03-21",
    "year": "2023",
    "pubDate": "2023-03-21T00:00:00",
    "number": 3361,
    "urn": "urn:nbn:de:0074-3361-0",
    "archive": "http://sunsite.informatik.rwth-aachen.de/ftp/pub/publications/CEUR-WS/Vol-3361.zip",
    "desc": "?",
    "h1": "SwissText 2022 Swiss Text Analytics Conference 2022",
    "volume_number": "Vol-3361",
    "ceurpubdate": "2023-03-21",
    "voltitle": "Swiss Text Analytics Conference 2022",
    "homepage": "https://www.swisstext.org/",
    "h3": "Proceedings of the Swiss Text Analytics Conference 2022",
    "colocated": null
  }