Update README_zh.md

README_zh.md

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 # RT-Thread #
 
+[![GitHub release](https://img.shields.io/github/release/RT-Thread/rt-thread.svg)](https://github.com/RT-Thread/rt-thread/releases)
 [![Build Status](https://travis-ci.org/RT-Thread/rt-thread.svg)](https://travis-ci.org/RT-Thread/rt-thread)
 [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/RT-Thread/rt-thread?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![GitHub pull-requests](https://img.shields.io/github/issues-pr/RT-Thread/rt-thread.svg)](https://github.com/RT-Thread/rt-thread/pulls)
+[![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat)](https://github.com/RT-Thread/rt-thread/pulls)
 
 RT-Thread是一个来自中国的开源物联网操作系统，它提供了非常强的可伸缩能力：从一个可以运行在ARM Cortex-M0芯片上的极小内核，到中等的ARM Cortex-M3/4/7系统，甚至是运行于MIPS32、ARM Cortex-A系列处理器上功能丰富系统。