feat: Mail sent on newsletter subsciption

[Ayesha-Siddiqua88]

Implement the feature to send a confirmation email when a user subscribes to the newsletter. This ensures users are informed of their successful subscription and enhances user engagement by providing immediate feedback. This functionality will be implemented using emailjs. The mail will say something like "Thank you for subscribing to VigyBag newsletter! We're excited to keep you updated with our latest news, insights, and special offers. Stay tuned for more!"

@codervivek5 , please assign this to me under GSSoC'24