feat(isLuhnValid): Expose isLuhnValid independently from isCreditCard

[ST-DDT]

Currently the luhn checking algorithm is only used inside isCreditCard, but the luhn algorithm is also used in/for other "numbers", so it would be nice if the isLuhnValid could be exposed independently.

is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the United States, Canadian Social Insurance Numbers, Israeli ID Numbers, South African ID Numbers, Swedish National identification numbers, Swedish Corporate Identity Numbers (OrgNr), Greek Social Security Numbers (ΑΜΚΑ), SIM card numbers and survey codes appearing on McDonald's, Taco Bell, and Tractor Supply Co. receipts.

Source: https://en.wikipedia.org/wiki/Luhn_algorithm

The code is copied from the existing isCreditCard check.

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable) - Tests from isCreditCard apply, if any exist.

[codecov]

Codecov Report

Merging #1974 (4098467) into master (cfcf911) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1974   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          103       104    +1     
  Lines         2097      2104    +7     
  Branches       473       473           
=========================================
+ Hits          2097      2104    +7     

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

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[WikiRik]

isCreditCard is testing different aspects as well. Can you add special tests for isLuhnValid?

[ST-DDT]

isCreditCard is testing different aspects as well. Can you add special tests for isLuhnValid?

Done

[profnandaa]

Suggesting a rename to isLuhnNumber instead.