AMQP Exception marker interface is for Throwable types

This change fixes downstream `catch` mechanisms' type soundness, which rely on a `class-string<Throwable>` being used.

Author: Ocramius

PhpAmqpLib/Exception/AMQPExceptionInterface.php

@@ -2,6 +2,8 @@
 
 namespace PhpAmqpLib\Exception;
 
-interface AMQPExceptionInterface
+use Throwable;
+
+interface AMQPExceptionInterface extends Throwable
 {
 }