Gets the currently-selected font features.
Use [class@Gtk.FontDialog] and [class@Gtk.FontDialogButton] instead
The format of the returned string is compatible with the [CSS font-feature-settings property](https://www.w3.org/TR/css-fonts-4/
font
-rend-desc). It can be passed to [func@Pango.AttrFontFeatures.new].
this |
a `GtkFontChooser` |
the currently selected font features |