Add note to Active Storage guide about S3 permissions [ci skip]

guides/source/active_storage_overview.md

@@ -121,6 +121,8 @@ Add the [`aws-sdk-s3`](https://github.com/aws/aws-sdk-ruby) gem to your `Gemfile
 gem "aws-sdk-s3", require: false
 ```
 
+NOTE: The core features of Active Storage require the following permissions: `s3:ListBucket`, `s3:PutObject`, `s3:GetObject`, and `s3:DeleteObject`. If you have additional upload options configured such as setting ACLs then additional permissions may be required.
+
 ### Microsoft Azure Storage Service
 
 Declare an Azure Storage service in `config/storage.yml`: