Regex validation for email during signup process

[Eddges]

Description

** Regex validation for email in the signup form. The program throws an alert and doesn't proceed to registration.

Motivation and Context

** During user registration, it is possible currently to sign up with an invalid email. I felt adding an email validation with a tried and tested regular expression so the form doesn't accept invalid email might be a good addition.

How Has This Been Tested?

** The regex is based on RFC822 standard, so it covers the entire spectrum of email addresses. I have used the regex from w3resources. So it is expected to work right.
I tested the same code with camicroscope. It works for all the cases. I have used the same code in my earlier projects and it has never caused an issue.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[birm]

Thank you, this should hopefully help avoid some confusion