Added neopixel rainbow example

examples/neopixel-rainbow.py

@@ -0,0 +1,17 @@
+import time
+import board
+import digitalio
+import neopixel
+from adafruit_led_animation.animation.rainbow import Rainbow
+
+pixel_pin = board.GP28
+num_pixels = 1
+brightness = 0.2
+
+
+pixels = neopixel.NeoPixel(pixel_pin, num_pixels, brightness=brightness, auto_write=False)
+
+rainbow = Rainbow(pixels, 0.01, period=10)
+
+while True:
+    rainbow.animate()