Consider providing the same signature as Edge functions

[TooTallNate]

For the Deno runtime, I decided a while back to standardize on implementing one syntax for users to define their HTTP handler code, and that syntax was to match Edge functions (i.e. export default (req: Request) => Response | Promise<Response>).

This signature represents the ideal "Vercel syntax" IMO, and if we can keep it standardized between all supported JS runtimes, then it would make interoperability easier.