New resource: github_user_email_address

[arunsathiya]

Resolves https://github.com/integrations/terraform-provider-github/issues/2070

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Before the change?

• It is not possible to create/read/destroy an email address to/from the GitHub user account.

After the change?

• It is possible to create/read/destroy an email address.

Pull request checklist

• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• [ ] Yes
• [x] No

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[github-actions[bot]]

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