Adding a field checker to discard malicious script code in email field

[harshit-soora]

Adding a field checker to discard malicious script code in email field of 'signup.html' page

Fixes #553

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream master branch.
• The unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

• All the functions created/modified in this PR contain relevant docstrings.

Short description of what this resolves:

This checks the text written in the email field of the signup.html is an email or not

Changes proposed in this pull request:

-This pull request strengthen the signup.html for Cross Site Scripting Attacks