Gets the `PangoFontFace` representing the selected font group details (i.
Use [class@Gtk.FontDialog] and [class@Gtk.FontDialogButton] instead
e. family, slant, weight, width, etc).
If the selected font is not installed, returns null.
this |
a `GtkFontChooser` |
A `PangoFontFace` representing the selected font group details |