test to try to get doc working

Revision:
2:d96d40a3858c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Sat Mar 28 12:06:41 2020 +0000
@@ -0,0 +1,1 @@
+https://github.com/armmbed/mbed-os/#0fdfcf7350896a9c0b57c4a18237677abfe25f1a