Refactor email validation regex to RFC 5322-compliant implementation

[afislonge]

PR Description:

This PR refactors the email validation logic in the repository to use a more comprehensive regex that aligns with common RFC 5322 patterns and stricter domain rules.

Changes Include

• Replaced the old simple regex with a new RFC 5322-based regex.

• Added support for:

  • Quoted local parts (e.g., "john.doe"@example.com)
  • Stricter domain validation (no leading/trailing hyphens, no consecutive dots)
  • Valid TLD lengths (2–63 characters)
  • IPv4/IPv6 literal domains (e.g., user@[192.168.0.1])

• Updated README.md to reflect the refactored implementation and examples.

• Added test cases for both common valid and invalid email formats.

Pull Request Checklist

Overview

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• I have read and understood the CONTRIBUTING.md guidelines
• My pull request has a descriptive title that accurately reflects the changes and the description has been filled in above.
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• I've created a new branch in my forked repository for this contribution

Code Quality

• My code is relevant to ServiceNow developers
• My code snippets expand meaningfully on official ServiceNow documentation (if applicable)
• I've disclosed use of ES2021 features (if applicable)
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