Enhancement: Add use statement (intercom#327)

Co-authored-by: Gabriel Anca Corral <[email protected]>

Author: OskarStark

README.md

@@ -73,6 +73,8 @@ $client->setUriFactory($yourUriFactory);
 This library is intended to work with any API Version. By default, the version that you have configured for your App in the [Developer Hub](https://developers.intercom.com/) will be used. However, you can overwrite that version for a single request or for all the requests using this library by including the `Intercom-Version` header when initializing the client as follows:
 
 ```php
+use Intercom\IntercomClient;
+
 $client = new IntercomClient(
     '<insert_token_here>',
     null,