manual's translation of zh-CN version

[Yeegsing]

Summary

I translate the manual into zh-CN.

How it was tested?

I follow the instruction of how to build the manual locally, and webstie turns out work properly.

[Wilfred]

Awesome! I just need to figure out how to deploy this so people can access both versions, and then I can merge this :)

[Yeegsing]

Hi Wilfred, I checkout mdBook's User Guide, however it seems that mdBook hasn't supported multilingual feature yet. Besides, I find a PR dealing with multilingual feature and here's an example using that fork.
If you think this is worth a try, I can try it on my local machine first. 😃

[Wilfred]

OK, this is now deployed at https://difftastic.wilfred.me.uk/zh-CN/ :)

@Yeegsing would you like to add a pull request on the English manual with a link to this one for Chinese readers? I would do it myself, but I don't speak Chinese.