feat(isLicensePlate): add es-AR license plate validator

[alvarocastro]

Added validation regex for Argentina license plates whose format can be AB 123 CD or ABC 123.

Checklist

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

[codecov]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage 👍

Coverage data is based on head (3476598) compared to base (531dc7f).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2103   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          104       104           
  Lines         2308      2309    +1     
  Branches       578       578           
=========================================
+ Hits          2308      2309    +1     

Impacted Files	Coverage Δ
src/lib/isLicensePlate.js	100.00% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[WikiRik]

Do you have a source on this?

[alvarocastro]

Do you have a source on this?

I live in Argentina, couldn't find any "official" source, but here is a wikipedia article: https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_Argentina

This validator supports:

• The old format "ABC 123" (specific for Argentina) that it's still valid but not issued anymore and;
• The new format "AB 123 CD" which is the current Argentine standard (actually is the standard for all the Mercosur countries).

[profnandaa]

LGTM, thanks for your PR. I'll fix the merge conflict in the release.

[profnandaa]

combined in #2164