Add FlockingArrows generative art application

[eightohnine]

Created a new Processing sketch that implements flocking behavior with arrow-shaped objects. Features include:

• Arrow class with Boids algorithm (separation, alignment, cohesion)
• Interactive mouse controls (avoid, attract, repel)
• Dynamic flock size adjustment
• Trailing visual effects
• Screenshot capability

The arrows respond to mouse movement and clicks, creating an engaging generative art experience.