Add Success Message to Newsletter Form

[akshay0611]

📌 Issue Description

The newsletter subscription form currently lacks user feedback upon successful submission. A success message should appear after the user submits their email, confirming that they have successfully subscribed.

✅ Expected Outcome

• A success message should appear after submitting a valid email.
• The message should disappear automatically after a few seconds.
• The form should reset after submission.
• Basic email validation should be implemented.

🏗 Suggested Solution

Modify the HTML, CSS, and JavaScript to include a success message that appears after form submission.