docs: product analytics

**Description**

I'm currently implementing product analytics using [mixpanel](https://pub.dev/packages/mixpanel_flutter) (however, the particular analytics solution shouldn't matter too much). I already read the docs regarding [`BlocObserver`](https://bloclibrary.dev/#/coreconcepts?id=blocobserver) but are there additional docs or example apps showing how to track and process events?

I'm also curious about how VGV is doing product analytics. I'd love to hear about your best practices 👍🏻

**Context**
The idea of using a `BlocObserver` to do the tracking is simple: This way we have easy access to all the emitted events and can just ingest them into our analytics solution. In addition, we do not need to clutter `Bloc` code with an additional `AnalyticsRepository`. However, depending on the event the `BlocObserver` approach might also track data we do not want to have in our analytics solution (e.g. password data from a `PasswordChanged` event). Therefore, we are looking to exclude some of the events or properties.

Since there are a few options to accomplish excluding events and/or properties I'm asking for best practices to guide our decision.

Thanks in advance