Custom fonts on mobile

Mobile users cannot set custom fonts or fallback fonts and so may not view text content not supported by an official fallback font. As such they are not able to participate as fully as desktop users in communities who use text not renderable by built-in fonts.

Allow mobile users to add a font to the fonts list that can be used to render text that is not renderable by built-in fonts.

This is particularly effects communities who use conscripts, such as the Toki Pona community.