Add arena barriers

[cdsupina]

Barriers are in place on the boundary of the window (we can move the side ones in when we add the side panels). Had a chance to explore the colliders and rigidbodies with rapier. Noteable changes:

• Added four barriers on edges of window
• Gave barriers and player zero friction
• Gave barriers and player 1.0 restitution (bounciness)
• Locked rotation of player
• Made barriers static rigidbodies and the player a dynamic rigidbody

[tigleym]

Very nice! This works really nicely.