[修改] 增加freeRTOS

1. 版本FreeRTOSv202212.01，命名为kernel；

kernel/FreeRTOS/README.md

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+## Directories:
+
++ The **FreeRTOS/Source** directory contains the FreeRTOS source code, and contains
+  its own readme file.
+
++ The **FreeRTOS/Demo** directory contains a demo application for every official
+FreeRTOS port, and contains its own readme file.
+
++ The **FreeRTOS/Test** directory contains the tests performed on common code and the portable layer code, and contains its own readme file.
+
+See [FreeRTOS/SourceOrganization](http://www.freertos.org/a00017.html) for full details of the directory structure and information on locating the files you require.
+
+The easiest way to use FreeRTOS is to start with one of the pre-configured demo
+ application projects (found in the FreeRTOS/Demo directory).  That way you will
+have the correct FreeRTOS source files included, and the correct include paths
+configured.
+Once a demo application is building and executing you can remove
+the demo application file, and start to add in your own application source
+files.
+
+### See also -
++ [Quick Start Guide](http://www.freertos.org/FreeRTOS-quick-start-guide.html)
+
++ [FAQ](http://www.freertos.org/FAQHelp.html)