Add php-ext to array dumper

src/Composer/Package/Dumper/ArrayDumper.php

@@ -37,6 +37,7 @@ class ArrayDumper
             'devAutoload' => 'autoload-dev',
             'notificationUrl' => 'notification-url',
             'includePaths' => 'include-path',
+            'phpExt' => 'php-ext',
         ];
 
         $data = [];

tests/Composer/Test/Package/Dumper/ArrayDumperTest.php

@@ -234,6 +234,11 @@ class ArrayDumperTest extends TestCase
                 ['ssl' => ['local_cert' => '/opt/certs/test.pem']],
                 'transportOptions',
             ],
+            [
+                'php-ext',
+                ['extension-name' => 'test'],
+                'phpExt',
+            ],
         ];
     }
 }