fix: don't strip :root pseudo-class

[asgerb]

This PR adds the :root pseudo-class to BAD_PSEUDO_FUNCTIONS, so it doesn't get stripped from the output CSS.

I've needed this to retain custom properties defined for my stylesheets.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cea4110) 97.84% compared to head (ae77e8a) 97.85%.

❗ Current head ae77e8a differs from pull request most recent head 7189178. Consider uploading reports for the commit 7189178 to get more accurate results

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #173   +/-   ##
=======================================
  Coverage   97.84%   97.85%           
=======================================
  Files          57       57           
  Lines        1994     2002    +8     
=======================================
+ Hits         1951     1959    +8     
  Misses         43       43           

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[Mange]

Looks really great! Thank you for your contribution! ❤️

Would you mind adding yourself to the Changelog under the "dev" heading as part of this PR? You can credit yourself how you want your name to appear. You can look at the other examples in the file to get an idea on how to do it.

[asgerb]

Certainly, just added it now 🙂

[Mange]

Version 5.2.1 was just released with this fix included.