Sample project needs updating to Flutter 3

[Stef-GMS]

This current project is setup for Flutter 2, per README.md. This project needs to be updated to Flutter 3 (at the time of this submission, the current version is 3.7.8 (released in Jan 2023).

Flutter 3, 3.3, and 3.7 released a lot of changes.

Also, analysis_options.yaml needs to be updated to remove unnecessary lint rules that are included in flutter_lints now included when one does flutter create

[suragch]

@VegetarianZombie Did you see this as well as PR #9?