Support for additional structure types for PDF tagging

[PRGfx]

When checking a document with <code> tags, I noticed that they are just represented as span. There seems to be a matching structure type – I'm not aware whether it might have been a later addition – but I don't see it used in the PdfBoxAccessibilityHelper. Is this the correct place to look? Browsing a bit through the code I don't see how to customize or subclass this. Is there a way to do this?