Update README

Author: algoliareadmebot

README.md

@@ -857,6 +857,8 @@ You can use the following optional arguments:
 
 <p>Attributes are separated with a comma (for example <code>&quot;name,address&quot;</code>). You can also use a string array encoding (for example <code>[&quot;name&quot;,&quot;address&quot;]</code> ). By default, all attributes are retrieved. You can also use <code>*</code> to retrieve all values when an <strong>attributesToRetrieve</strong> setting is specified for your index.</p>
 
+<p><code>objectID</code> is always retrieved even when not specified.</p>
+
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