Bundled assistant-ui dependency

Gram Elements now bundles the assistant-ui dependency internally rather than externalizing it.

This change simplifies the installation process and reduces potential version conflicts when integrating Gram Elements into existing projects. The library is now more self-contained, making it easier to get started.

Features

• Bundled assistant-ui - The assistant-ui dependency is no longer externalized, simplifying installation and reducing peer dependency requirements.
• Install script - Added an install script to the Elements package for easier setup.

Bug fixes

• Changelog fixes - Resolved issues with the Elements changelog that prevented proper updates in previous releases.