Add new GHES Packages storage warning (#16439)

* Add new warning

* Apply suggestions from code review

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: Lucas Costi <lucascosti@users.noreply.github.com>

Co-authored-by: Lucas Costi <lucascosti@users.noreply.github.com>

Author: jmarlena

content/admin/packages/configuring-third-party-storage-for-packages.md

@@ -21,7 +21,10 @@ For the best experience, we recommend using a dedicated bucket for {% data varia
 
 {% warning %}
 
-**Warning:** Make sure to configure the bucket you'll want to use in the future. We do not recommend changing your storage after you start using {% data variables.product.prodname_registry %}.
+**Warnings:**
+- It's critical you set the restrictive access policies you want for your storage bucket because {% data variables.product.company_short %} does not apply specific object permissions or additional access control lists (ACLs) to your storage bucket configuration. For example, if you make your bucket public, data in the bucket will be accessible on the public internet. For more information, see [Setting bucket and object access permissions](https://docs.aws.amazon.com/AmazonS3/latest/user-guide/set-permissions.html) in the AWS Documentation.
+- We recommend using a dedicated bucket for {% data variables.product.prodname_registry %}, separate from the bucket you use for {% data variables.product.prodname_actions %} storage.
+- Make sure to configure the bucket you'll want to use in the future. We do not recommend changing your storage after you start using {% data variables.product.prodname_registry %}.
 
 {% endwarning %}