fix ReDOS in isEmail and isHSL

[tux-tn]

This PR updates isEmail and isHSL in order to prevent ReDOS attack described in #1597 and #1598 without changing the behaviour of both validators.

mocha has also been updated to the latest version in order to prevent npm/yarn audit from displaying a warning (Mocha is used as a dev dependency, people using validator are not impacted)

Checklist

• PR contains only changes related; no stray files, etc.

[codecov]

Codecov Report

Merging #1651 (f967d0a) into master (05ceb18) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1651   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          100       101    +1     
  Lines         1847      1854    +7     
=========================================
+ Hits          1847      1854    +7     

Impacted Files	Coverage Δ
src/lib/isEmail.js	100.00% <100.00%> (ø)
src/lib/isHSL.js	100.00% <100.00%> (ø)
src/lib/isIBAN.js	100.00% <0.00%> (ø)
src/lib/isMobilePhone.js	100.00% <0.00%> (ø)
src/lib/isPassportNumber.js	100.00% <0.00%> (ø)
src/lib/util/typeOf.js	100.00% <0.00%> (ø)

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[profnandaa]

Thanks for getting this in! LGTM.