fix(isSlug & rtrim): regex no longer exposed to ReDOS attacks

[fedeci]

This should be merged after #1602
Regexes are updated in order not to change their behaviour, but only their logic.

Fixes #1596 and fixes #1599

Checklist

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

[codecov]

Codecov Report

Merging #1603 (9a7f773) into master (1b85829) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1603   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          100       100           
  Lines         1796      1798    +2     
=========================================
+ Hits          1796      1798    +2     

Impacted Files	Coverage Δ
src/lib/isPassportNumber.js	100.00% <ø> (ø)
src/lib/isDataURI.js	100.00% <100.00%> (ø)
src/lib/isIdentityCard.js	100.00% <100.00%> (ø)
src/lib/isMACAddress.js	100.00% <100.00%> (ø)
src/lib/isSlug.js	100.00% <100.00%> (ø)
src/lib/isStrongPassword.js	100.00% <100.00%> (ø)
src/lib/rtrim.js	100.00% <100.00%> (ø)

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[tux-tn]

LGTM 🎉 thank you for spotting and fixing the ReDOS

[profnandaa]

Thanks for the fix!