Import spandrel_extra_arches if present.

I will not add this dependency to the default ones because models in the
spandrel_extra_arches package are non commercial and therefore not
compatible with free software licenses like the one ComfyUI uses.

If you don't mind this you can install it manually yourself.

comfy_extras/nodes_upscale_model.py

 import os
+import logging
 from spandrel import ModelLoader, ImageModelDescriptor
 from comfy import model_management
 import torch
 import comfy.utils
 import folder_paths
 
+try:
+    from spandrel_extra_arches import EXTRA_REGISTRY
+    from spandrel import MAIN_REGISTRY
+    MAIN_REGISTRY.add(*EXTRA_REGISTRY)
+    logging.info("Successfully imported spandrel_extra_arches: support for non commercial upscale models.")
+except:
+    pass
+
 class UpscaleModelLoader:
     @classmethod
     def INPUT_TYPES(s):