3.0.0 Beta4

Major Release 3.0.0 Beta4🛠️

⚠️ This is a major beta release that contains breaking API changes.
See the full list of changes along with step-by-step guides to upgrade.
https://documentation.onesignal.com/docs/mobile-2020-api-migration-guide

❓ Please provide feedback and bug reports with the beta version included in the title to this repo's issue tracker.
https://github.com/OneSignal/OneSignal-Flutter-SDK/issues

Some highlights for this release

• Fix launch URL always returning null on Android #398
• Upgrade from Android version 4.3.3 to 4.4.0
  • See full release notes https://github.com/OneSignal/OneSignal-Android-SDK/releases
• Upgrade from iOS version 3.4.3 to 3.4.4
  • See full release notes https://github.com/OneSignal/OneSignal-iOS-SDK/releases
• Update pod file to use XCFramework