add pole balancing example

examples/pole_balancing/config.ini

@@ -0,0 +1,7 @@
+[NeuralNetwork]
+num_inputs = 4
+num_outputs = 2
+
+[Evolution]
+max_fitness = 500
+max_generations = 20

examples/pole_balancing/pole_balancing.py

@@ -0,0 +1,39 @@
+import gymnasium as gym
+import sys
+import os
+import numpy as np
+
+sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
+
+from sneat import evolve
+
+def fitness(genome, render=False):
+    env = gym.make('CartPole-v1', render_mode='human' if render else 'rgb_array')
+
+    fitnesses = []
+    for _ in range(20):
+        fitness = 0
+
+        obs, info = env.reset()
+        while True:
+            obs = list(obs)
+            action = genome.activate(obs)
+            action = np.argmax(action)
+            obs, reward, terminated, truncated, info = env.step(action)
+
+            fitness += reward
+
+            if terminated or truncated:
+                break
+
+        fitnesses.append(fitness)
+
+    env.close()
+    return np.mean(fitnesses)
+
+def main():
+    winner = evolve(fitness)
+    fitness(winner, render=True)
+
+if __name__ == '__main__':
+    main()