added io4/GO cms

Added io4/GO cms.

Used by several Dutch local governments:
https://borsele.gemeenteoplossingen.nl
www.gemeente-steenbergen.nl
www.gemeentenoordenveld.nl
www.demarne.nl
The developer has several versions of io4 cms and a special local government version called GO cms.
This regex currently catch both as it's unclear if there is a technical difference.
I don't believe the `|` need escaping. The `+` also seems superfluous?