Write a proximity-aware Mbed-based LED scanner!

Revision:
1:9bb81732ca15
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Thu Nov 29 18:50:07 2018 +0000
@@ -0,0 +1,1 @@
+https://github.com/armmbed/mbed-os/#2fd0c5cfbd83fce62da6308f9d64c0ab64e1f0d6