add Adafruit Feather nRF52840 Sense to doc

Author: dglaude

docs/index.rst

@@ -28,6 +28,7 @@ Table of Contents
 
     Adafruit CircuitPlayground Bluefruit <https://www.adafruit.com/product/4333>
     Adafruit CLUE nRF52840 Express <https://www.adafruit.com/product/4500>
+    Adafruit Feather nRF52840 Sense <https://www.adafruit.com/product/4516>
 
 .. toctree::
     :caption: Other Links