Add success message functionality to hero form on successful email submission

[akshay0611]

Problem:

The current hero form does not show any feedback or success message to users after they submit their email address. This leaves users uncertain about whether their action was successful.

Solution:

Implement a success message that appears after the user successfully submits their email through the hero form. The message will confirm the submission and then disappear after a short delay.

Changes:

• Added a hidden success message div to the HTML.
• Display the success message after a successful form submission.
• Clear the input field after successful submission.
• Hide the success message after 3 seconds.

Expected Result:

When the user submits the hero form with a valid email address, they should see a success message saying "Thank you! Your email has been successfully submitted." The message should disappear after 3 seconds, and the input field should be cleared.