The author property is deprecated in favor of [verified publishers](https://dart.dev/tools/pub/publishing#create-verified-publisher).

Corrects the following issues from the analyzer:

* info • Avoid using braces in interpolation when not needed • example/lib/main.dart:41:59 • unnecessary_brace_in_string_interps
* info • Avoid using braces in interpolation when not needed • example/lib/main.dart:50:46 • unnecessary_brace_in_string_interps

This addresses issues found in the analyzer similar to:

   info • The operand can't be null, so the condition is always false • example/lib/main.dart:130:16 • unnecessary_null_comparison

Fixes issues raised by the analyzer similar t:

* info • Unused import: 'package:flutter/foundation.dart' • lib/src/create_notification.dart:2:8 • unused_import
   info • The import of 'package:onesignal_flutter/src/notification.dart' is unnecessary because all of the used elements are also provided by the import of
* 'package:onesignal_flutter/onesignal_flutter.dart' • lib/src/create_notification.dart:3:8 • unnecessary_import