Create Emails class for email validation and uniqueness

[Emine0010]

Implement an Emails class to validate and store unique email addresses.

Describe your changes

Checklist

• I have read the [CONTRIBUTING]
• I have performed a self-review of my own code
• I have run the code locally and it works as expected
• I have commented my code, particularly in hard-to-understand areas

Screenshots (if appropriate)