v2.1.0

This is an automated PR for a new release.

Please check the following before approving:

• Changelog is accurate. The documented changes for this release are printed below.
• Any files referencing a version number. Confirm it matches the version number in the branch name.

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Release Changelog Preview

v2.1.0

Features

• Update new_client_from_environment() to support optional token parameter, matching URL parameter behavior. {#88}

Fixes

• Fix get_item() to successfully retrieve items with 26-character titles by adding fallback to title search when ID lookup fails. {#80}
• Updated Slack developer link in documentation. {#130}