feat(isMobilePhone): add Saint Vincent locale

[MapleQiAN]

Summary

• add en-VC mobile phone validation for Saint Vincent and the Grenadines
• add valid and invalid test cases
• document en-VC in the isMobilePhone locale list

Refs #1761

Validation

• npm test

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (7fdc788) to head (de812ed).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2707   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2587      2587           
  Branches       656       656           
=========================================
  Hits          2587      2587           

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