fix(isRgbColor): allow longer alpha decimal precision

[Hashim1999164]

Summary

• Update isRgbColor alpha regex so values like 0.123 and 1.00 are accepted, matching CSS <alpha-value> (unrestricted <number> precision).
• Adjust tests: move previously rejected multi-decimal alphas into the valid set and add cases from isRgbColor: alpha values with more than 2 decimal digits or trailing zeros on '1' are incorrectly rejected #2792.

Fixes #2792

Test plan

• npm test -- --grep "should validate rgb color"
• Confirm rgba(0,0,0,1.00) and rgba(0,0,0,0.123) return true

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (ce62eb4) to head (c69667e).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2825   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2587      2587           
  Branches       656       656           
=========================================
  Hits          2587      2587           

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