Add bootstrap to maintain old root namespace alias.

Since we don't want to introduce a BC Break on the first day, we must
maintain the existence of the LeanPHP namespace even if we moved forward.

Author: shulard

composer.json

@@ -58,7 +58,10 @@
     "autoload": {
         "psr-4": {
             "FriendsOfPhpSpec\\PhpSpec\\CodeCoverage\\": "src/"
-        }
+        },
+        "files": [
+            "src/bootstrap.php"
+        ]
     },
     "minimum-stability": "stable",
     "scripts": {

src/bootstrap.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of the friends-of-phpspec/phpspec-code-coverage package.
+ *
+ * @author  shulard <s.hulard@chstudio.fr>
+ * @license MIT
+ *
+ * For the full copyright and license information, please see the LICENSE file
+ * that was distributed with this source code.
+ */
+use FriendsOfPhpSpec\PhpSpec\CodeCoverage\CodeCoverageExtension;
+
+\class_alias(
+    CodeCoverageExtension::class,
+    'LeanPHP\PhpSpec\CodeCoverage\CodeCoverageExtension'
+);