add readme for qwiic stuff

drivers/qwiic/readme.md

@@ -0,0 +1,7 @@
+# Qwiic Devices
+
+[More info on Sparkfun's Qwiic Connect System](https://www.sparkfun.com/qwiic)
+
+Currently supported devices:
+
+* [Joystiic](https://www.sparkfun.com/products/14656)