perf(isISO31661Alpha2): use a Set along with .has instead of includes

[jmpaya]

perf(isISO31661Alpha2): use a Set along with .has instead of includes
fix(isBIC): refactor use of CountryCodes using Set's methods

Updated isISO31661Alpha2 to use a Set along with .has to reduce complexity from O(n) to O(1) as stated here.
Updated isBIC to use Set's methods instead of Array's.

Checklist

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

[codecov]

Codecov Report

Merging #1724 (bd1757c) into master (8c4b3b3) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1724   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          101       101           
  Lines         2005      2005           
  Branches       452       452           
=========================================
  Hits          2005      2005           

Impacted Files	Coverage Δ
src/lib/isBIC.js	100.00% <100.00%> (ø)
src/lib/isISO31661Alpha2.js	100.00% <100.00%> (ø)

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[tux-tn]

Thank you, nice catch!
LGTM 🎉

[profnandaa]

LGTM too, thanks for your contrib!