Add success message to hero form on successful submission

[akshay0611]

What does this PR do?

This PR adds a success message to the hero form, which appears after a successful email submission. It enhances the user experience by providing clear feedback upon form submission. It closes Issue no #3

Changes:

• Updated the HTML structure to include a success message div.
• Implemented JavaScript to display the success message when the form is submitted successfully.
• Cleared the input field after form submission.
• Added a timeout to hide the success message after 3 seconds.

How to Test:

1. Open the page containing the hero form.
2. Enter a valid email address and submit the form.
3. A success message should appear saying "Thank you! Your email has been successfully submitted."
4. The success message should disappear after 3 seconds, and the email input should be cleared.

Additional Notes:

• This functionality improves form feedback and ensures users are aware that their submission was successful.

Screenshot after the changes