feat(isMobilePhone): add Cape Verde (pt-CV) mobile phone validation

[singhvishalkr]

I noticed Cape Verde (Cabo Verde) was missing from the isMobilePhone validator so I added support for it.

Cape Verde uses country code +238 with 7-digit mobile numbers. Mobile numbers start with 91-99 or 59.

References:

• ITU National Numbering Plan for Cape Verde: https://www.itu.int/oth/default.aspx?lang=en&parent=T0202000026

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7fdc788) to head (088ac9a).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2710   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          114       114           
  Lines         2587      2587           
  Branches       656       656           
=========================================
  Hits          2587      2587           

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