Add Chinese translations

[rgommers]

This integrates the Crowdin translations into master, fixes a number of rendering issues, and makes Chinese translations show up in PR previews (but not yet on numpy.org, we haven't launched yet).

In the PR preview it is now easy to see where there are still gaps in translations.

Note, to build the site locally with translations, use:

export NUMPYORG_WITH_TRANSLATIONS=1
python gen_config.py
hugo
hugo server

[rgommers]

Showing up now in preview:

[Qiyu8]

The news page has been override by @InessaPawson 's "Make an announcement about the 2021 NumPy survey", Not only the Chinese translation is affected, but the translation of other languages is also affected. should we fix this content? It's looks like the translation process is conflicted with document maintenance.

[melissawm]

Ah, I think this is what I mentioned at #55 (comment)

[charris]

What is the status of this?

[rgommers]

What is the status of this?

It's kind of stuck on lack of bandwidth from me to finish it. Merging this PR seems not too far off; just one review comment to deal with. Actually launching the translations on the public site is a bit more involved - and also I'm expecting that we'll get a larger amount of contributions at that point, and I at least have no bandwidth to respond to them at the moment. @InessaPawson and I talked recently about how to get translations moving; it'll take a few months probably.