Release current state (machine translated version) as a preview version

[HyunggyuJang]

I guess the demand for translation became obsolete among d2l maintainers. It has been about 2 years from the last update; this fact discourages potential contributors to attempt to work on this repo.

My suggestion is to release machine translated version, the current master branch of this repo as preview version, following http://preview.d2l.ai/d2l-en/master/.