common/u*: add Chinese translation

[BananaaaKING]

1. u3d.md
2. ufraw-batch.md
3. ugrep.md
4. ulimit.md
5. umask.md
6. umount.md
7. unclutter.md
8. uncrustify.md
9. unexpand.md
10. unimatrix.md
11. uniq.md
12. unison.md
13. unlink.md
14. unp.md
15. unrar.md
16. unset.md
17. unzstd.md
18. updog.md
19. upt.md
20. upx.md
21. users.md
22. usql.md
23. uudecode.md
24. uuencode.md
25. uv-python.md
26. uv-tool.md
27. uv.md
28. uvicorn.md

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR title conforms to the recommended templates.