Support onLoad event for FileReader #330
Description
In MDN, FileReader has a event called onLoad, but unfortunately in current main b55f343, there is no such event to listen to.
Current workaround would need to write a custom Extension Method, mimic the the onLoadEnd event which is currently inside main
extension on FileReader {
Stream<ProgressEvent> get onLoad =>
EventStreamProviders.loadEvent.forTarget(this);
}