Added norm freezing doc

README.md

@@ -141,6 +141,8 @@ Images are resized to 640x640 pixels and rescaled with `image_mean=[0.485, 0.456
 
 ![image/png](https://cdn-uploads.huggingface.co/production/uploads/6579e0eaa9e58aec614e9d97/E15I9MwZCtwNIms-W8Ra9.png)
 
+Freezing BN is `True` by default for R18 and R34 versions due to backwards compatibility. But in the original implementation the value is `False`.
+Set `freeze_backbone_batch_norms=False` for original model behaviour.
 
 ## Evaluation