feat(isMobilePhone): add (en-CM) alias for Cameroon (fr-CM) mobile phone validation

[JossGeek]

What I did

Added mobile phone validation for Anglophone Cameroon (en-CM)
to the isMobilePhone validator.

Changes

• Added en-CM alias in src/lib/isMobilePhone.js
• Added valid and invalid test cases in test/validators.test.js

References

• Cameroon country code: +237
• All mobile operators numbers.
• Source simple localize
• Source ICU Locale

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 (e36b279) to head (e714c5c).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2701   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2586      2587    +1     
  Branches       656       656           
=========================================
+ Hits          2586      2587    +1     

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[rubiin]

reference should be a link

[JossGeek]

@rubiin I've just added a link as reference.

[Copilot]

Pull request overview

Adds support for validating Cameroon mobile phone numbers under the en-CM locale for isMobilePhone.

Changes:

• Added en-CM locale support by aliasing it to the existing fr-CM phone pattern.
• Added en-CM valid/invalid test fixtures for isMobilePhone.
• Updated README documentation to include en-CM in the isMobilePhone locale list (plus additional formatting changes).

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/lib/isMobilePhone.js	Adds en-CM as an alias of the existing fr-CM regex.
test/validators.test.js	Adds en-CM test coverage with representative valid/invalid numbers.
README.md	Updates the documented isMobilePhone locale list to include en-CM (and reflows related markdown).

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated 2 comments.

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