Add PAM model and Updated Crowd Demo

What's Changed

• Init Predictive Avoidance Model by @m-brandon-haworth in #5

New Contributors

• @m-brandon-haworth made their first contribution in #5

Full Changelog: 0.0.2-alpha...v0.0.3-alpha

Refactored API

This extension now serves as a simple demo for the crowds backend.

• Full refactoring of interface
• Examples folder showing various call methods
• Simulator class can handle updates or users can get positions/forces back to update themselves

Forces Fix

Fixes a bug to the zero vector which caused wavy movements.

Initial Release

Basic social forces without environment detection/repulsion forces.