v0.5.0-alpha

Full Changelog: v0.4.0-alpha...0.5.0-alpha

• Added previous actions to player struct, will remove previous action from reward function and observation builder likely soon because of this
• Fixed tester.rs import
• Fixed bug regarding previous action not updating to fit a new number of agents
• Mapped car ids to always be from 1 to 6 in the gym instead of getting them directly from RocketSim which kept ticking up forever when removing and adding new cars