Add warning to CORS section.

Documenting an important Caveat with CORS.

Author: csteegz

articles/machine-learning/how-to-deploy-and-where.md

@@ -1165,6 +1165,10 @@ def run(request):
 > pip install azureml-contrib-services
 > ```
 
+> [!WARNING]
+> Azure Machine Learning will only route POST and GET requests to the containers running the scoring service. 
+> This can cause errors due to browsers using OPTIONS requests to pre-flight CORS requests. 
+
 ## Next steps
 
 * [How to deploy a model using a custom Docker image](how-to-deploy-custom-docker-image.md)