feat: Add Success Message to Newsletter Subscription Form

[akshay0611]

Summary:
This PR adds a success message to the newsletter subscription form to improve user feedback. After a user submits the form, a success message is displayed to confirm their request.

Changes Made:

• Added a hidden success message element (<p class="success-message">) below the form.
• Included JavaScript to handle form submission and display the success message dynamically.
• Ensured the form fields are cleared after submission for a clean user experience.

Testing:

• Verified that the success message appears after form submission.
• Tested responsiveness across different screen sizes.
• Ensured alignment with existing CSS styles and framework conventions.

Related Issue:
Closes #16

[Imran-imtiaz48]

Summary:
This PR enhances the newsletter subscription form by providing user feedback upon successful submission. A success message is displayed after the form is submitted, improving user experience.
Changes Made:
• Implemented an event listener for form submission to prevent default behavior.
• Displayed a success message dynamically when the form is submitted.
• Reset the form fields after submission for a cleaner user experience.
• Added a timeout to hide the success message after 5 seconds.
Testing:
• Verified that the success message appears after form submission.
• Ensured the message disappears after the set timeout.
• Checked form behavior across different browsers and screen sizes.
• Ensured compatibility with existing styles and layout conventions.