changelog updated

Author: antonpirker

CHANGELOG.md

@@ -1,5 +1,25 @@
 # Changelog
 
+## 3.0.0a3
+
+We're excited to announce that version 3.0 of the Sentry Python SDK is now
+available. This release is the result of a long-term effort to use OpenTelemetry
+under the hood for tracing. This switch opens the door for us to leverage the
+full power of OpenTelemetry, so stay tuned for more integrations and features
+in future releases.
+
+Looking to upgrade from Sentry SDK 2.x to 3.x? See the
+[full list of changes](MIGRATION_GUIDE.md) for a comprehensive overview
+of what's changed. Looking for a more digestible summary? See the
+[migration guide in the docs](https://docs.sentry.io/platforms/python/migration/2.x-to-3.x)
+with the most common migration patterns.
+
+⚠️ This is a pre-release. If you feel like taking it for a spin, we'd be grateful
+for your feedback. How was the migration? Is everything working as expected? Is
+*nothing* working as expected? Something in between? Please let us know
+[on GitHub](https://github.com/getsentry/sentry-python/discussions/3936) or
+[on Discord](https://discord.com/invite/Ww9hbqr).
+
 ## 3.0.0a2
 
 We're excited to announce that version 3.0 of the Sentry Python SDK is now