docs(sage_invoice): Add django.contrib.humanize app to the required apps

README.md

@@ -86,6 +86,7 @@ Add `django-sage-invoice` to your `INSTALLED_APPS` in the Django settings and co
 ```python
 INSTALLED_APPS = [
     # other packages
+    "django.contrib.humanize",
     "django_jsonform",
     "import_export",
     "sage_tools",