v0.1.0 of whisperr

Official Whisperr SDK for Flutter — identify users and track product events to power churn-prevention interventions. Changelog excerpt: - Initial release. - Whisperr.initialize, identify, track, flush, reset. - Durable, ordered outbound queue with batched delivery (/v1/events/batch), offline persistence, exponential-backoff retry, and 429/auth/client-error handling. - App-lifecycle flush on pause/detach.