docs: add CONTRIBUTING.md with Releasing section (#916)

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: aaronsteers

CONTRIBUTING.md

@@ -0,0 +1,9 @@
+# Contributing
+
+Thank you for your interest in contributing to the Airbyte Python CDK!
+
+## 🚀 Releasing
+
+This project uses [`semantic-pr-release-drafter`](https://github.com/aaronsteers/semantic-pr-release-drafter) for automated release management. To release, simply click "`Edit`" on the latest release draft from the [releases page](https://github.com/airbytehq/airbyte-python-cdk/releases), and then click "`Publish release`". This publish operation will trigger all necessary downstream publish operations.
+
+ℹ️ For more detailed instructions, please see the [Releasing Guide](https://github.com/aaronsteers/semantic-pr-release-drafter/blob/main/docs/releasing.md).