fix World.show_network() file path error

Author: toruseo

uxsim/uxsim.py

@@ -2524,6 +2524,9 @@ def show_network(W, width=1, left_handed=1, figsize=(6,6), network_font_size=10,
         node_size : int, optional
             The size of the nodes in the visualization. Default is 6.
         """
+        
+        os.makedirs(f"out{W.name}", exist_ok=True)
+
         plt.rcParams["font.family"] = get_font_for_matplotlib()
 
         plt.figure(figsize=figsize)