Use a seperate repo for docs' translations

[awxiaoxian2020]

I notice that there are many volunteers want to add translations for docs. It will be hard to maintain.

[posva]

So far it seems fine. The main issue is the API docs are generated from the source code. Not sure if that will work when using a different repository

[awxiaoxian2020]

@posva The en docs are generated from the source code indeed. But the zh docs seem only a copy of en docs even now. It seems not to relate to source code. We can re-build using vitepress with locale doc contents.