fix: handle stdio properly

README.md

@@ -11,7 +11,7 @@ use Nih\CommandBuilder\Stdio;
 require_once __DIR__ . '/vendor/autoload.php';
 
 $child = (new Command('/usr/bin/cat'))
-    ->stdin(Stdio::piped('r'))
+    ->stdin(Stdio::piped())
     ->spawn(shell: false);
 
 $child->stdin?->write('Hello, this is pretty cool.');