feat(isPostalCode): Add postal code for Monaco

[moogblob]

Main postal code is 98000. 98001 - 98099 is used for "special types of delivery".

https://en.wikipedia.org/wiki/Postal_codes_in_France#Monaco

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 (b1aea75) to head (e69230a).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2682   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          114       114           
  Lines         2595      2595           
  Branches       659       659           
=========================================
  Hits          2595      2595           

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[saiding619]

nice