fix(isRgbColor): allow more than one decimal on alpha

[marcopixel]

The current regex is only allowing for one decimal on the alpha value even though the specification has no limit on maximal decimals.

I've adjusted the regex + the tests accordingly and it does pass now if it has more than one decimal if set as number between 1 and 0.

References

https://www.w3.org/TR/css-color-3/#transparency

<alphavalue>: Syntactically a <number>.

https://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-number

A <number> can either be an <integer>, or it can be zero or more digits followed by a dot (.) followed by one or more digits

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)
• References provided in PR (where applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (4197b86) to head (a75a9cd).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2378   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          107       107           
  Lines         2449      2449           
  Branches       619       619           
=========================================
  Hits          2449      2449           

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[marcopixel]

Sorry, i've just noticed that this is a duplicate of #2346 - the difference between these two pull requests is that mine doesn't limit to a second decimal point.

[WikiRik]

Let's discuss that difference in #2346