Add Simplified Chinese localization

[calcitem]

:scroll: Description

Add translations for Simplified Chinese language.

:bulb: Motivation and Context

Although we have used the delegate interface provided by this package to implement language extensions in our projects, it is possible that other users will not do this, so we added a new language.

:green_heart: How did you test it?

The modification is obvious, so it has not been verified for the time being.

:pencil: Checklist

• [x] I reviewed submitted code
• [ ] I added tests to verify changes
• [ ] I updated the docs if needed
• [ ] All tests passing
• [x] No breaking changes

:crystal_ball: Next steps

• Delete files that do not need to be included in version control from the repository.
• It is recommended to use the arb files to manage these strings.

[codecov[bot]]

Codecov Report

Merging #157 (45f20dd) into master (583b502) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #157   +/-   ##
=======================================
  Coverage   85.59%   85.59%           
=======================================
  Files          21       21           
  Lines         590      590           
=======================================
  Hits          505      505           
  Misses         85       85           

Impacted Files	Coverage Δ
feedback/lib/src/l18n/translation.dart	68.18% <ø> (ø)

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[ueman]

Thanks!