Add success message to contact form

[akshay0611]

Summary: This feature adds a success message to the contact form, which will appear after a successful form submission.

Changes Made:

• Added a success message ("Your message has been sent successfully!") below the form that appears when the form is successfully submitted. The success message will be visible for 3 seconds before disappearing.

This change enhances the user experience by providing feedback after a form submission, confirming that the message has been sent successfully.