Conditionally compile out the implementation of `EventHandler::new` when using the N-API backend, since that's not yet implemented.
Conditionally compile out the implementation of `EventHandler::new` when
using the N-API backend, since that's not yet implemented.

rustbridge/neon,neon-bindings/neon,rustbridge/neon,rustbridge/neon,neon-bindings/neon,neon-bindings/neon,rustbridge/neon,neon-bindings/neon,rustbridge/neon,rustbridge/neon