[Feature] Add Onboarding flow

[hrideshmg]

Is your feature request related to a problem? Please describe.
Right now the status for a particular session is set by single tap (for bunk), double tap (for cancel), and long press (for present).
This is not immediately obvious to a user using the app for the first time.

Describe the solution you'd like
A guided tour of the status status explaining the behaviour for different types of presses should be presented to a new user. One relevant package might be: https://pub.dev/packages/onboarding_overlay

Describe alternatives if applicable
Any method of teaching the user the different behaviour's is acceptable