Variable Fonts Support

Add support for variable fonts where we can set custom weight, width, slant, etc.

We could embed only one font file and change the parameters for each text style that we need in the preset. That would give us a smaller preset file size and theoretically endless customization possibilities when it comes to text & typography.

The text item properties will have to be redesigned to make room for all the possible settings, and so would the font picker activity, so that we can preview customization options even before selecting a font.

Support for variable fonts is available from Android O, investigating if there are ways of working around this

Any update on support for variable fonts? I have fonts I want to use that are variable so I currently can't use them in KWGT