add attributes to readme

Author: julesterrien

README.md

@@ -24,6 +24,9 @@ Called when the requested script is fully loaded.
 ### `url` (required)
 URL pointing to the script you want to load.
 
+### `attributes`
+An object used to define custom attributes to be set on the script element. For example, `attributes={{ id: 'someId', 'data-custom: 'value' }}` will result in `<script id="someId" data-custom="value" />`
+
 ## Example
 You can use the following code to load jQuery in your app: