Add App Tutorial

[Khaoz-Topsy]

Is your feature request related to a problem? Please describe. The app is quite complex and people keep missing features that already exist

Describe the solution you'd like A page that shows initially when a user opens the app and can be started from the settings page. This page would describe what the app can do etc

Additional context https://pub.dev/packages/feature_discovery https://pub.dev/packages/intro_slider