fix: adding explicit content

Author: JulesEmond

CommunityToolkit.WinUI.UI.Controls.Markdown/MarkdownTextBlock/MarkdownTextBlock.xaml

@@ -100,7 +100,8 @@
                     <Border x:Name="RootElement"
                             Background="{TemplateBinding Background}"
                             BorderBrush="{TemplateBinding BorderBrush}"
-                            BorderThickness="{TemplateBinding BorderThickness}" />
+                            BorderThickness="{TemplateBinding BorderThickness}"
+                            Content="{TemplateBinding Content}" />
                 </ControlTemplate>
             </Setter.Value>
         </Setter>