Add sleep to RGB example

Author: bennuttall

examples/rgb.py

@@ -1,5 +1,6 @@
 from tree import RGBXmasTree
 from colorzero import Color
+from time import sleep
 
 tree = RGBXmasTree()
 
@@ -9,5 +10,6 @@
     while True:
         for color in colors:
             tree.color = color
+            sleep(1)
 except KeyboardInterrupt:
     tree.close()