feat: first impl

example.php

@@ -0,0 +1,26 @@
+<?php
+
+use Nih\CommandBuilder\Command;
+use Nih\CommandBuilder\Stdio;
+
+require_once __DIR__ . '/vendor/autoload.php';
+
+$output = (new Command('echo'))
+    ->arg('-n')
+    ->arg('-')
+    ->arg("./ \$wow     '''/stdout.txt")
+    ->stderr(Stdio::null())
+    ->output();
+
+var_dump($output);
+
+$child = (new Command('/usr/bin/cat'))
+    ->stdin(Stdio::piped('r'))
+    ->spawn(shell: true);
+
+$child->stdin?->write('Hello, this is pretty cool.');
+$child->stdin?->close();
+
+$output = $child->output();
+
+var_dump($output);