Allow for providerToken and campaignToken

 providerToken (from the app) and the a campaignToken, people can attribute the installs in ASC

```swift
let config = SKOverlay.AppConfiguration(appIdentifier: advert.appStoreID, position: .bottom)
config.userDismissible = true
config.campaignToken = "CAMPAIGN_TOKEN"
config.providerToken = "PROVIDER_ID"
```