Refactor: add color type helper

[thadeucity]

A color object type is being checked the same way in 3 parts of the code. hslToColorString.js , rgbToColorString.js and toColorString.js. To simplify its use and also reduce the lib size, a helper function was created to identify the color object type.

The refactoring reduced the lib size by approximately 0.7% (Gziped) It is a marginal gain, but I believe any size improvement is a welcome one.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (a7e3dee) to head (108c170).

:exclamation: Current head 108c170 differs from pull request most recent head 019893c. Consider uploading reports for the commit 019893c to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #625   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           89        90    +1     
  Lines          860       847   -13     
  Branches       323       301   -22     
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- Hits           860       847   -13     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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