编写翻译贡献指导说明

[WillemJiang]

为了帮助实习生，志愿者能够更好地参与翻译，需要在README文档中列出详细的贡献指南。
可以参考 Envoy的翻译文档README https://github.com/cloudnativeto/envoy/blob/zh/docs/root/README.md

[sunshinemingo]

I want to have a try.

[WillemJiang]

@sunshinemingo， it's greate. Please go ahead and feel free to submit PR for it.
@hanyouqing could you help @sunshinemingo by reviewing her PR?

[WillemJiang]

#27 @hanyouqing 已经提交了一部分的内容到doc中。 @sunshinemingo 可以看一下。