Add link to RTOS + Sphere sample

Author: liydu

README.md

@@ -18,4 +18,10 @@ this repository:
 
 NOTE: These zip files are completely self-contained and include appropriate
 code from the other Azure RTOS repositories. Please refer to the LICENSE.txt file
-in each ZIP file for licensing requirements.
+in each ZIP file for licensing requirements.
+
+### Azure RTOS with Azure Sphere sample
+
+https://github.com/Azure-Samples/Azure-RTOS-on-Azure-Sphere-Mediatek-MT3620
+
+This sample demonstrates how Azure Sphere and Azure RTOS are able to run together on the MediaTek MT3620 Development Kit.