Update README.md

README.md

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 [中文页](README_zh.md) |
 
+[![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 is an open source IoT operating system from China, which has strong scalability: from a tiny kernel running on a tiny core, for example ARM Cortex-M0, or Cortex-M3/4/7, to a rich feature system running on MIPS32, ARM Cortex-A8, ARM Cortex-A9 DualCore etc.