feat(*): Add self-play RL training pipeline with PPO trainer, in-game GDScript policy inference, and bot opponent support in Match mode

Game/addons/godot_rl_agents/rewards/RewardFunction3D.gd

@@ -0,0 +1,10 @@
+extends Node3D
+class_name RewardFunction3D
+
+
+func get_reward():
+	return 0.0
+
+
+func reset():
+	return