Add license/copyright file headers to index.php and index.php.dist

index.php

@@ -1,4 +1,14 @@
 <?php // @codingStandardsIgnoreFile
+/**
+ * This file is part of Pico. It's copyrighted by the contributors recorded
+ * in the version control history of the file, available from the following
+ * original location:
+ *
+ * <https://github.com/picocms/Pico/blob/master/index.php>
+ *
+ * SPDX-License-Identifier: MIT
+ * License-Filename: LICENSE
+ */
 
 // load dependencies
 if (is_file(__DIR__ . '/vendor/autoload.php')) {

index.php.dist

@@ -1,4 +1,14 @@
 <?php // @codingStandardsIgnoreFile
+/**
+ * This file is part of Pico. It's copyrighted by the contributors recorded
+ * in the version control history of the file, available from the following
+ * original location:
+ *
+ * <https://github.com/picocms/Pico/blob/master/index.php.dist>
+ *
+ * SPDX-License-Identifier: MIT
+ * License-Filename: LICENSE
+ */
 
 // check PHP platform requirements
 if (PHP_VERSION_ID < 50306) {