MarkdownTextBlock: Expose MarkdownDocument as a readonly property#613

Arlodotexe merged 2 commits intoCommunityToolkit:mainCommunityToolkit/Labs-Windows:mainfrom

jcoc611-microsoft:user/juosori/Markdown_Readonly_Documentjcoc611-microsoft/Labs-Windows:user/juosori/Markdown_Readonly_DocumentCopy head branch name to clipboard