feat(isNumeric): add support for thousand separator option

[PepiPetrov]

This fixes #1433 and resolves merge conflicts of #1476 .

Checklist

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

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 99.96%. Comparing base (7fdc788) to head (9deb113).

Files with missing lines	Patch %	Lines
src/lib/isNumeric.js	85.71%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #2711      +/-   ##
===========================================
- Coverage   100.00%   99.96%   -0.04%     
===========================================
  Files          114      114              
  Lines         2587     2593       +6     
  Branches       656      659       +3     
===========================================
+ Hits          2587     2592       +5     
- Partials         0        1       +1     

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