update doc

Author: skywind3000

README.md

@@ -1,6 +1,6 @@
 # RenderHelp
 
-:zap: 可编程渲染管线实现，全中文注释，帮助初学者学习渲染原理 
+:zap: 可编程渲染管线实现，全中文注释，帮助初学者学习渲染原理。
 
 [![GitHub license](https://img.shields.io/github/license/Naereen/StrapDown.js.svg)](https://github.com/Naereen/StrapDown.js/blob/master/LICENSE) [![Maintenance](https://img.shields.io/badge/Maintained%3F-yes-green.svg)](https://GitHub.com/Naereen/StrapDown.js/graphs/commit-activity) [![Join the chat at https://gitter.im/skywind3000/asynctasks.vim](https://badges.gitter.im/skywind3000/asynctasks.vim.svg)](https://gitter.im/skywind3000/RenderHelp?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)