Add reference to link to register list.

tannewt · tannewt · commit a9226a3ffd27 · 2017-01-05T18:33:44.000-08:00
diff --git a/adafruit_register/index.rst b/adafruit_register/index.rst
@@ -1,3 +1,5 @@
+.. _register-module-reference:
+
 Module Reference
 ================
 
