Update for Markdown.Xaml

I’ve updated my Markdown.Xaml project with some new capabilities.

The most significant change is the ability to use WPF styles to control the presentation of the generated flow document. Unlike HTML, where you link the stylesheet to the HTML after rendering, the WPF approach requires you to hook the styles up to the Markdown.Xaml rendering engine, which in turn hooks the styles up to the generated document as it works.

A new demo application shows how to use WPF styles along with the rendering engine, along with a new TextToFlowDocumentConverter that has proven useful in my own applications.

See the Markdown.Xaml project on GitHub for all the juicy details.