Deprecate smp branch (#799)

* Update deprecation message in README.md

Author: chinglee-iot

README.md

@@ -1,3 +1,17 @@
+# ![image](https://user-images.githubusercontent.com/56273942/202568467-0ee721bb-1424-4efd-88fc-31b4f2a59dc6.png) DEPRECATED
+
+## Announcement:
+
+FreeRTOS SMP feature has been merged into [FreeRTOS-Kernel](https://github.com/FreeRTOS/FreeRTOS-Kernel/commit/ae3a498e435cecdb25b889f2740ea99027dd0cb1) main branch. We recommend you to use the [FreeRTOS-Kernel](https://github.com/FreeRTOS/FreeRTOS-Kernel/commit/ae3a498e435cecdb25b889f2740ea99027dd0cb1) main branch to develop FreeRTOS SMP applications.
+
+The contents of this branch will remain available for certain period but we will no longer provide updates or accept new contributions and pull requests.
+
+Have more questions? Post them in the [FreeRTOS forum](https://forums.freertos.org/).
+
+
+
+---
+
 ## Getting started
 This repository contains FreeRTOS kernel source/header files and kernel ports only. This repository is referenced as a submodule in [FreeRTOS/FreeRTOS](https://github.com/FreeRTOS/FreeRTOS) repository, which contains pre-configured demo application projects under ```FreeRTOS/Demo``` directory.