feat: Add support for Feather M0

One belt is an M0 instead of 32u4, because there were not enough
32u4s in stock at the time.

platformio.ini

@@ -8,10 +8,21 @@
 ; Please visit documentation for the other options and examples
 ; http://docs.platformio.org/page/projectconf.html
 
+[platformio]
+env_default = feather32u4
+
 [env:feather32u4]
 platform = atmelavr
 board = feather32u4
 framework = arduino
 lib_deps =
   Adafruit BluefruitLE nRF51
-  FastLED
+  FastLED
+
+[env:adafruit_feather_m0]
+platform = atmelsam
+board = adafruit_feather_m0
+framework = arduino
+lib_deps =
+  Adafruit BluefruitLE nRF51
+  FastLED