Merge pull request #4 from prcutler/root-group-fix

Update display.root_group for CP 9 compatibility

Author: dhalbert

examples/tt21100_paint.py

@@ -25,7 +25,7 @@
 tg = displayio.TileGrid(pixels, pixel_shader=palette)
 g = displayio.Group()
 g.append(tg)
-display.show(g)
+display.root_group = g
 
 while True:
     for point in tt.touches: