- Added error classes for various SMTP-related issues (ConnectionError, AuthenticationError, etc.) in `errors.ts`.
- Created main entry point for the SMTP over WebSocket client library in `index.ts`, exporting client, types, errors, and transport.
- Developed Nodemailer transport adapter for SMTP over WebSocket in `transport.ts`, including methods for sending mail and verifying transport configuration.
- Defined type definitions for the SMTP over WebSocket protocol in `types.ts`, including message types, connection states, and client configuration options.
