Add information about the services repo

Author: paul-szczepanek-arm

connectivity/FEATURE_BLE/include/ble/services/services.md

@@ -0,0 +1,13 @@
+# Mbed OS BLE services
+
+BLE services are available in the https://github.com/ARMmbed/mbed-os-experimental-ble-services repository. It's a
+community effort and contains services created by mbed-os team, our partners and mbed-os users. 
+
+To use the services there add the repository to your project by adding a 'mbed-os-experimental-ble-services.lib' file
+containing the link to the repo like so:
+```
+https://github.com/ARMmbed/mbed-os-experimental-ble-services
+```
+
+Each BLE service is an Mbed OS library.  To use it with new cmake based mbed-tools you will need to add the library
+to your link libraries for your application.