Add aws canned acl docs

Author: pditommaso

docs/config.rst

@@ -542,6 +542,7 @@ Advanced client configuration options can be set by using the ``client`` attribu
 =========================== ================
 Name                        Description
 =========================== ================
+acl                         Allow the setting of a predefined bucket permissions also known as *canned ACL*. Permitted values are ``Private``, ``PublicRead``, ``PublicReadWrite``, ``AuthenticatedRead``, ``LogDeliveryWrite``, ``BucketOwnerRead``, ``BucketOwnerFullControl`` and ``AwsExecRead``. See `Amazon docs <https://docs.aws.amazon.com/AmazonS3/latest/userguide/acl-overview.html#canned-acl>`_ for details.
 connectionTimeout           The amount of time to wait (in milliseconds) when initially establishing a connection before giving up and timing out.
 endpoint                    The AWS S3 API entry point e.g. `s3-us-west-1.amazonaws.com`.
 maxConnections              The maximum number of allowed open HTTP connections.