Fixed example output for list-buckets --details

README.md

@@ -241,7 +241,8 @@ Add `--details` to include details of the bucket ACL, website configuration and
 Using `--details` adds three additional API calls for each bucket, so it is advisable to use it with one or more explicit bucket names.
 ```
 % s3-credentials list-buckets simonw-test-public-website-bucket --details
-{
+[
+  {
     "Name": "simonw-test-public-website-bucket",
     "CreationDate": "2021-11-08 22:53:30+00:00",
     "bucket_acl": {
@@ -269,7 +270,8 @@ Using `--details` adds three additional API calls for each bucket, so it is advi
         "Key": "error.html"
       }
     }
-}
+  }
+]
 ```
 A bucket with `public_access_block` might look like this:
 ```json