feat: add static helper class for license constants (#15)

This PR adds a new class for holding license constants, which is read by extensions like LibreJS to check that the site contains free JavaScript code.

Reviewed-on: https://codeberg.org/vlw/scaffold/pulls/15

src/Helpers/License.php

@@ -0,0 +1,34 @@
+<?php
+
+	namespace vlw\Scaffold\Helpers;
+
+	class License {
+		public const MAGNET_END = PHP_EOL . "// @license-end";
+
+		public const GPL_V3_MAGNET = "// @license magnet:?xt=urn:btih:1f739d935676111cfff4b4693e3816e664797050&dn=gpl-3.0.txt GPL-v3-or-Later";
+		public const GPL_V3_BLOCK = "<script><!--//--><![CDATA[//><!--
+			/**
+			 * @licstart The following is the entire license notice for the JavaScript
+			 * code in this page.
+			 *
+			 * Copyright (C) 2020  Free Software Foundation.
+			 *
+			 * The JavaScript code in this page is free software: you can redistribute
+			 * it and/or modify it under the terms of the GNU General Public License
+			 * (GNU GPL) as published by the Free Software Foundation, either version 3
+			 * of the License, or (at your option) any later version.  The code is
+			 * distributed WITHOUT ANY WARRANTY; without even the implied warranty of
+			 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU GPL
+			 * for more details.
+			 *
+			 * As additional permission under GNU GPL version 3 section 7, you may
+			 * distribute non-source (e.g., minimized or compacted) forms of that code
+			 * without the copy of the GNU GPL normally required by section 4, provided
+			 * you include this license notice and a URL through which recipients can
+			 * access the Corresponding Source.
+			 *
+			 * @licend The above is the entire license notice for the JavaScript code
+			 * in this page.
+			 */
+		//--><!]]></script>";
+	}