feat: add CustomerIORouteObserver for optimized route tracking

[AristideVB]

Summary

This PR introduces CustomerIORouteObserver, a route observer that automatically tracks screen views and reports them to Customer.io. The observer integrates seamlessly with GoRouter or MaterialApp, thus eliminating the need for manual tracking logic.

Changes

• Implemented CustomerIORouteObserver that extends NavigatorObserver.
• Integrated the observer with GoRouter.
• Removed manual route tracking and listeners.

This PR aims to address Issue #87

[Shahroz16]

The PR was very valuable, thank you for creating it. They will be bundled up with some of the other changes in the pipeline, that are going to affect the public-facing APIs.

[AristideVB]

Thanks @Shahroz16 looking forward, for this update ? Why not merge my PR thought ? If you are going to use the code ? 🙂

(Or suggest edits if needed)

[Shahroz16]

@AristideVB thank you again for the efforts here, really appreciate it. We are updating public APIs, and sample apps with the bigger change in question, we haven't decided yet, but we might expose a class for tracking which would be optional.

Once we have all the details figured out, if we are to use this code, we will merge the PR as it is, otherwise, we will make related changes wherever needed.