The .po files have been created for zh_CN and are now available on Weblate. If you prefer not to use Weblate and intend to submit translations via a Pull Request, your language files can be found on the next-release branch in _translator-files/po/zh_CN/.
Please consult this README file for more information on the translation process.
Add files for Chinese (simplified) as requested by @yangyangdaji.