add: php composer management

vendor/composer/installers/src/bootstrap.php

@@ -0,0 +1,18 @@
+<?php
+
+use Composer\Autoload\ClassLoader;
+
+function includeIfExists(string $file): ?ClassLoader
+{
+    if (file_exists($file)) {
+        return include $file;
+    }
+
+    return null;
+}
+if ((!$loader = includeIfExists(__DIR__ . '/../vendor/autoload.php')) && (!$loader = includeIfExists(__DIR__ . '/../../../autoload.php'))) {
+    die('You must set up the project dependencies, run the following commands:'.PHP_EOL.
+        'curl -s http://getcomposer.org/installer | php'.PHP_EOL.
+        'php composer.phar install'.PHP_EOL);
+}
+return $loader;