fix: [CheckboxStory] responsive layout

[Juyeong-Byeon]

Description

I found a small style problem in checkboxStory Component and fixed it.

Before:

1. There is no flexWrap option in Wrapper component so in mobile environment some checkbox won't show
2. There is no key props for LabelWrapper, so there are warnings while compiling code

After:

1. Added flexWrap:'wrap' and justifyContent:'center' for responsive layout
2. Added key props for LabelWrapper

Related Issues

X

Tests

X

Checklist

Before you create this PR confirms that it meets all requirements listed below by checking the relevant checkboxes ([x]). This will ensure a smooth and quick review process.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• Run yarn test or yarn test -u if you need to update snapshot.
• Run yarn lint
• I am willing to follow-up on review comments in a timely manner.

[codecov]

Codecov Report

Merging #61 (4df40c6) into master (ab9bf3f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #61   +/-   ##
=======================================
  Coverage   93.94%   93.94%           
=======================================
  Files          21       21           
  Lines         545      545           
  Branches      236      236           
=======================================
  Hits          512      512           
  Misses         33       33           

[hyochan]

LGTM!