Immediately disconnect the port. Calling disconnect() on an
already-disconnected port has no effect. When a port is disconnected, no
new events will be dispatched to this port.
Fired when the port is disconnected from the other end(s).
runtime.lastError may be set if the port was disconnected by an error.
If the port is closed via $(ref:Port.disconnect disconnect), then this
event is only fired on the other end. This event is fired at most once
(see also Port lifetime).
This property will only be present on ports passed to
$(ref:runtime.onConnect onConnect) / $(ref:runtime.onConnectExternal
onConnectExternal) / $(ref:runtime.onConnectExternal onConnectNative)
listeners.