v0.2.1: Enable Google Cloud Storage support for object_store

SlateDB's `all` feature doesn't include GCP support since it lacks a
`gcp` feature. Add object_store directly with the `gcp` feature to
enable GCS URL parsing. Bump version to 0.2.1.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

v0.2.0: Bump version to 0.2.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

v0.1.1

Fix published entrypoint and add ATTW package test