fix: options' className overwriting default styles instead of extending them

[stoil-terziev]

Fixes #75

Currently, options are being spread after className, causing any option defined with custom className to lose the default styles.

[codecov]

Codecov Report

Merging #175 (152e92b) into master (c39fdc9) will not change coverage.
The diff coverage is n/a.

❗ Current head 152e92b differs from pull request most recent head 0fccbc0. Consider uploading reports for the commit 0fccbc0 to get more accurate results

@@           Coverage Diff           @@
##           master     #175   +/-   ##
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  Coverage   99.13%   99.13%           
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  Files           2        2           
  Lines         115      115           
  Branches       26       26           
=======================================
  Hits          114      114           
  Misses          1        1           

Impacted Files	Coverage Δ
src/index.tsx	98.21% <ø> (ø)

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[afc163]

https://github.com/react-component/segmented/releases/tag/v2.2.2