Gets the Standard 14 font whose metrics this font uses, or null. A Type 1 or TrueType font that is not
embedded uses them when its BaseFont is one of the fourteen names, or another name producers use for one of them
(such as Arial,Bold for Helvetica-Bold, recorded as an information diagnostic).
public Standard14Font? Standard14 { get; }
ISO 32000-2 §9.6.2.2.