add zh_cn - Githubissues

added zh_cn language

Submitter Checklist:

[ ] There is a ticket for my issue
[x] Wrote a good PR/commit description
[ ] Discussed about the issue with reviewers in Discussions, Issues or other platforms
[x] Confirmed that the PR only includes changes related to my issue
[ ] Checked the PR locally: flutter build windows (Request it to reviewers if you're having problems)