Promise that resolves with the HTTP server instance, with an added tunnel property of type TunnelInstance.
Remarks
This function provides a utility to expose an Express app or http.Server via a Pinggy tunnel.
It supports both Express applications and native Node.js http.Server instances.
Throws
Error if the input is not an Express app or http.Server, or if tunnel setup fails.
Starts an HTTP server (or uses an existing one) and exposes it via a Pinggy tunnel.