Update README with new features, usage guide, and file structure

[rebmoreno]

Summary

Updates the README to reflect the current state of the Ear2Earth project.

Changes

• Fixed typos in Purpose section
• Added new features to the Features section (undo/redo, export/import workspace, download CSV, clear workspace, metadata viewer, packet refresh, draggable toolbar, multi-axis visualization, global timeline, onboarding tour)
• Updated Quick Start steps to reflect current UI flow and added user guide link
• Updated Usage Guide with accurate data source flow, retrieval methods, and button labels
• Updated File Structure to reflect current repo
• Cleaned up Upcoming Features to current remaining items
• Added Acknowledgments and License to Table of Contents
• Fixed clone URL