Extensions do not support XML renderer

[nojb]

The extension API currently allows for custom LaTeX, man, HTML, CommonMark, plaintext render functions, but not for XML. Is there a good reason for this? I am using the XML backend but due to this I am not able to recognize GH extensions at that level.

[kivikakk]

No, it's probably just an oversight! I'd happily take a PR that adds this. (My work focus has shifted onto other priorities, unfortunately.)

[nojb]

Actually, it already works - I had notset up the syntax extensions correctly. Sorry for the noise!