Documentation clarification

[milesegan]

The usage example in the README calls the API this way:

void main() async {
  // Must add this line.
  WidgetsFlutterBinding.ensureInitialized();

  String feedURL = 'http://localhost:5002/appcast.xml';
  await autoUpdater.setFeedURL(feedURL);
  await autoUpdater.checkForUpdates();
  await autoUpdater.setScheduledCheckInterval(3600);

  runApp(MyApp());
}

But reading through the docs and the code it looks like the only thing actually necessary to enable the autoUpdater is this:

String feedURL = 'http://localhost:5002/appcast.xml';
await autoUpdater.setFeedURL(feedURL);

Calling checkForUpdates or setScheduledCheckInterval is not necessary for a basic working setup. Is that correct? If so maybe the docs could be expanded to make this more clear?

I'm happy to make a PR if this is correct.