New providers 🚀

Exciting release with 4 new provider:

• Email.js - Special thanks to @artfuldev
• nodemailer - Special thanks to @painotpi
• plivo
• postmark

Improvements ⭐️

• Added codespaces quick setup. Just press . on every PR to start developing quickly.
• Unified Provider response API. You will get the provider message identifier and the time stamp.
• A brand new theming API! Control the theme of your messages easily.

Other bug fixes and enhancements

Thanks to @SachinHatikankar100 and @L8Y for their contributions.