Add light control link to how_to_api.md

Add link to light control tutorial.

Author: Amanda Butler

docs/tutorials/using_apis/how_to_api.md

@@ -5,6 +5,7 @@ This section contains step-by-step tutorials that show you how to perform specif
 ### Connectivity
 
 - [TCP sockets](cellular-tcp-sockets.html).
+- [Light control using Mesh](../tutorials/light-control.html).
 - [BLE](ble-tutorial.html).
 - [LoRa Network](LoRa-tutorial.html).