Update settings-schema.json

I'd like to see a color-chooser included, so this is a suggested solution which works smoothly for me. Also requires changed "desklet.js" file which includes the new property (line 30) and a modified "_onSettingsChanged" function (line 42) .
Merge branch 'patch-1' of https://github.com/3n4rch3/Cinnamon into 3n4rch3-patch-1

Conflicts:
	files/usr/share/cinnamon/desklets/clock@cinnamon.org/settings-schema.json
Merge branch '3n4rch3-patch-1'