Add Chinese translation to the launcher (requires font support)

[hhyyrylainen]

Translation work on Chinese is done but when using it in the launcher, you get this:

Which is not the best so some kind of fallback font approach as used in Thrive is needed.

[hhyyrylainen]

I couldn't find a simple way to do this, but it should be possible according to:

• TextBox FontFamily FallBack AvaloniaUI/Avalonia#4708
• Port WPF's FormattedText to Avalonia and rework TextPresenter AvaloniaUI/Avalonia#4893

I think we might need to make it so that the viewmodel sets the font through a binding (and changing language needs to notify that that property has changed) which just checks which language is active and directly returns the fallback font resource.