Additions to the WinUI 3 built-in RichEditBox.
<dh:Win32RichEditBox xmlns:dh="using:Diahon.WinUI.Text">
<dh:Win32RichEditBox.ContextFlyout>
<dh:RichEditCommandBarFlyout />
</dh:Win32RichEditBox.ContextFlyout>
</dh:Win32RichEditBox>