Returns whether type is a standard structure type of this namespace.
public bool IsStandardType(string type)
The structure type name.
Em, Strong,
Title, H7 and the other PDF 2.0 additions are not standard in PDF 1.7, and Art, Note, Code and
the other PDF 1.7 types Annex M lists are not standard in PDF 2.0); for MathML, any non-empty name (element names are not checked
against the MathML 3.0 schema); for a custom namespace, false.
ISO 32000-2 §14.8.4, §14.8.6, Annex M; ISO/TS 32005 §5.3-§5.5.