azureblob: allow anonymous access for public resources

See: https://forum.rclone.org/t/azure-blob-public-resources/46882

docs/content/azureblob.md

@@ -289,6 +289,13 @@ be explicitly specified using exactly one of the `msi_object_id`,
 If none of `msi_object_id`, `msi_client_id`, or `msi_mi_res_id` is
 set, this is is equivalent to using `env_auth`.
 
+#### Anonymous {#anonymous}
+
+If you want to access resources with public anonymous access then set
+`account` only. You can do this without making an rclone config:
+
+    rclone lsf :azureblob,account=ACCOUNT:CONTAINER
+
 {{< rem autogenerated options start" - DO NOT EDIT - instead edit fs.RegInfo in backend/azureblob/azureblob.go then run make backenddocs" >}}
 ### Standard options