MarkdownToRtf

Converts a small Markdown subset into a StyledDocument, then to RTF via RtfWriter.

Supported subset:

• Paragraphs are separated by one or more blank lines.

• Inline bold: **text** or __text__.

• Inline italic: *text* or _text_.

• Combined bold+italic: ***text*** (or the ___text___ underscore form).

Headings, lists and links are out of scope: #, -, [ and friends are treated as literal text. An unmatched emphasis marker is emitted as a literal character rather than opening a span.