Provide PSR-11 exceptions

src/Exception/ContainerException.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace League\Container\Exception;
+
+use Psr\Container\ContainerExceptionInterface;
+use RuntimeException;
+
+class ContainerException extends RuntimeException implements ContainerExceptionInterface
+{
+}

src/Exception/NotFoundException.php

@@ -2,7 +2,7 @@
 
 namespace League\Container\Exception;
 
-use Interop\Container\Exception\NotFoundException as NotFoundExceptionInterface;
+use Psr\Container\NotFoundExceptionInterface;
 use InvalidArgumentException;
 
 class NotFoundException extends InvalidArgumentException implements NotFoundExceptionInterface