Document SDK initialization

[samhill303]

We want to have a very clear place where consuming apps initialize the SDK and do things like initialize the service locator. This should be documented and be clear in the code

[JuliaJakubcova]

Android:

• in onCreate in MainApp we call initAnalytics(AndroidAnalytics()) (and logging that the app started)
• and in module (koin module) we define the BreedRepository as single { AndroidServiceLocator(context = get()).breedRepository }.

iOS:

• in BrownfieldApp we initialize analytics in init() by AnalyticsKt.doInitAnalytics(analytics: IosAnalytics())
• and also in BrownfieldApp we define the view model private let serviceLocator: ServiceLocator = IOSServiceLocator(userDefaults: UserDefaults.standard)

[samhill303]

We should check if this is up to date and then add to the documentation