docs(README): add README

README.md

@@ -0,0 +1,32 @@
+# NIH PHP Command Builder
+
+Simple command builder inspired by rust's std library.
+
+```php
+<?php
+
+use Nih\CommandBuilder\Command;
+use Nih\CommandBuilder\Stdio;
+
+require_once __DIR__ . '/vendor/autoload.php';
+
+$child = (new Command('/usr/bin/cat'))
+    ->stdin(Stdio::piped('r'))
+    ->spawn(shell: true);
+
+$child->stdin?->write('Hello, this is pretty cool.');
+$child->stdin?->close();
+
+$output = $child->output();
+
+var_dump($output)
+
+// object(Nih\CommandBuilder\Output)#4 (3) {
+//   ["stdout"]=>
+//   string(27) "Hello, this is pretty cool."
+//   ["stderr"]=>
+//   string(0) ""
+//   ["code"]=>
+//   int(0)
+// }
+```