feature: add setup.php to configure manually installed applications

closes #578

setup.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * Run this script from the root directory of your WebEngine project.
+ * e.g. php vendor/phpgt/webengine/setup.php
+ *
+ * The purpose of this script is to make sure that the project is set up
+ * correctly, if it has been installed manually, rather than via the composer
+ * create-project command.
+ */
+$error = null;
+if(!is_dir("vendor")) {
+	if(!is_file("composer.json")) {
+		$error = "The current directory is not a WebEngine project.";
+	}
+	$error = "No vendor directory found - do you need to run `composer install`?";
+}
+if(is_file("build.default.json")) {
+	$error = "Please run this script from your project's root directory.";
+}
+if($error) {
+	echo "$error See https://www.php.gt/webengine/setup for more information.", PHP_EOL;
+	exit(1);
+}
+$indexPhpContents = <<<PHP
+<?php
+require(__DIR__ . "/../vendor/phpgt/webengine/go.php");
+PHP;
+
+if(!is_dir("www")) {
+	mkdir("www");
+}
+file_put_contents("www/index.php", $indexPhpContents);