docs: typo in filename

README.md

@@ -88,7 +88,7 @@ class CustomAdminClass(ModelAdmin):
 **Note:** Registered admin models coming from third party packages are not going to properly work with Unfold because of parent class. By default, these models are registered by using `django.contrib.admin.ModelAdmin` but it is needed to use `unfold.admin.ModelAdmin`. Solution for this problem is to unregister model and then again register it back by using `unfold.admin.ModelAdmin`.
 
 ```python
-# admin.opy
+# admin.py
 from django.contrib import admin
 from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
 from django.contrib.auth.models import User