Focus on officially support languages

[lamberta]

Hi all,

To make sustainable progress on this translations project in 2021, we're no longer accepting community contributions for languages without official support. As of now, the officially supported translations are: es-419, ja, ko, pt-br, and zh-cn.

Unofficial community-contributed languages have moved to the community branch and are not published on tensorflow.org: https://github.com/tensorflow/docs-l10n/tree/community/site

Thank you to everyone that has contributed translations and reviews to this project—the work is greatly appreciated! For some community languages this was a difficult decision, but ultimately comes down to building a sustainable process that accounts for document freshness, reviews, our automation pipeline, and even malicious content.

We will continue to add officially supported languages down the road, but will be more deliberate. And if your preferred language isn't officially supported, feel free to create a community fork for open source contributors and let us know!

Thanks,
Billy