feat: Validation for cambodia phone number added

[henrique73]

Created a regular expression to validate Cambodia phone numbers.
Added test cases to verify the correctness of the new regex pattern.
https://en.wikipedia.org/wiki/Telephone_numbers_in_Cambodia#:~:text=For%20example%2C%20012%20123%204567,is%20used%20by%20some%20operators.&text=Calls%20made%20from%20outside%20Cambodia%20must%20omit%20the%20prefix%200.,-Therefore%2C%20to%20call

-Issue
#2589

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 (6f436be) to head (e72244d).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2593   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          114       114           
  Lines         2536      2536           
  Branches       642       642           
=========================================
  Hits          2536      2536           

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