New settings item: SettingFontPicker

[maltfield]

This is a feature request to add a new built-in SettingItem in kivy for picking a font from the available system fonts.

The user should be able to select a font face and font size.

Why?

Kivy app developers should have a standardized way for users to pick fonts. This would be a great compliment to things like kivy.uix.colorpicker

Example UI

The interface should resemble other framework's "Font Picker" UIs, such as:

GTK's FontChooser

• https://docs.gtk.org/gtk3/iface.FontChooser.html

The FontChooser dialog in GTK

.NET FontDialog

• https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.fontdialog?view=windowsdesktop-8.0

The microsoft .NET FontDialog window