Composer: give credit where credit is due

The Package author still only mentioned "Jakub Onderka", while in reality other contributors should get credit for the work they have put in.

This is a relatively simple way to provide better credits.

composer.json

@@ -11,6 +11,10 @@
         {
             "name": "Jakub Onderka",
             "email": "ahoj@jakubonderka.cz"
+        },
+        {
+            "name" : "Contributors",
+            "homepage" : "https://github.com/php-parallel-lint/PHP-Parallel-Lint/graphs/contributors"
         }
     ],
     "require": {