Added bcc feature

[Nancy-byte]

• Used nodemailer for email services.
• Modified package.json file.
• Modified server/index.js
• Added server/src/config/nodemailer.js
• Added server/src/router/newsletter.js
• Modified .env.example to include necessary environment variables -Added bcc feature to hide the email ids of users

This commit includes the necessary configurations and routes to implement the Newsletter feature. Nodemailer is set up for sending emails, and the new routes handle the newsletter subscription and sending process.