href/link handling

[pkra]

There does not appear to be a way to activate links generated from href attributes in the source.

(There's also no non-visual indication for links but I think that's an upstream issue so I filed Speech-Rule-Engine/speech-rule-engine#251 upstream.)

[pkra]

As per F2F with @zorkow the non-visual indication is considered an upstream problem. SRE keeps the href attribute intact and thus it's up to the renderer (e.g. mathjax-a11y) to expose it correctly.