Vertical text support for TextBox/TextBlock/RichTextBox

Japanese can be written from [top-to-bottom, right-to-left](https://en.wikipedia.org/wiki/Japanese_language_and_computers#Direction_of_text). I would like to be able to present texts in this format in my WPF projects. Petty tricks like rotating the control won't give the [desired result](https://www.w3.org/International/articles/vertical-text/index).

Suggestion:
Add a new [FlowDirection](https://learn.microsoft.com/en-us/dotnet/api/system.windows.flowdirection) enum like "VerticalRightToLeft" that allows the aforementioned behavior.