Add simplified Chinese translation

[SouthFox-D]

Hi Prot,

Thanks for writing this book. I really got a lot out of reading it and have translated it into Chinese.
I was wondering if you'd be interested in seeing the Chinese translation?

[protesilaos]

Thank you @SouthFox-D!

I am not sure how we should manage such translations. Would they be in the same repository or in different ones?

One problem I see is with syncing changes between the languages. For example, I just made a small rewording to a heading: that would need to be reflected in the translations eventually. So I think it makes more sense to have each translation in its own Git repository.

[SouthFox-D]

@protesilaos

I've been paying attention to the one-to-one line correspondence in the translation, which might bring convenience to some automatic operation. However, I agree that separate repositories are a better option until we have a better solution.

If we do separate repositories, would you like to manage them, or create them by me, and you can simply refer to them?