MarkdownTextBlock sample should expose parsing/render options as checkboxes for sample exploration

> We should add a tracking issue to have the Markdown sample expose checkbox options for each of these settings properties so folks can see the behavior change in the output. (Though I think we'd have to make the control re-create the pipeline builder, I think they're all assumed to be set on initialization? Not 100% sure about that.) May be easier if we can switch to using the DependencyProperyGenerator later for all this stuff. :)

_Originally posted by @michael-hawker in https://github.com/CommunityToolkit/Labs-Windows/issues/674#issuecomment-2868009604_