[docs](readme)add hellogithub

README.md

@@ -13,6 +13,7 @@
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat)](https://github.com/RT-Thread/rt-thread/pulls)
 [![RT-Thread BSP Static Build Check](https://github.com/RT-Thread/rt-thread/actions/workflows/bsp_buildings.yml/badge.svg)](https://github.com/RT-Thread/rt-thread/actions/workflows/bsp_buildings.yml)
 
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 # RT-Thread
 
 RT-Thread was born in 2006, it is an open source, neutral, and community-based real-time operating system (RTOS).