translate UI to Chinese simplified.
I'm working in a translation to Chinese simplified, i believe soon i'll be able to submit a pull request for it.

Thanks to the community efforts, Simplified Chinese is now available in Mattermost 3.3!
Would you like to help re-tweet the announcement? https://twitter.com/mattermosthq/status/765566741921406976
We would like to invite you to join our translation server to help maintain the language, if you’d like (unless you’re already there): http://translate.mattermost.com/zh_CN/mattermost/