Build node graph rather than text in highlighter

[imitablerabbit]

Currently the text is being wrapped in span tags, this is fine until you have text which includes < and >. Then when .innerHtml is used to automatically parse the html tags from the text, it is also matching the < and > signs. An example of this is in the c++ include tests.

#include <vector>

Is turned into...

#include 

and a new html node <vector></vector> is created