add default value to config helper

Author: willyreyno

src/routes/routes.php

@@ -1,4 +1,4 @@
 <?php
 
-Route::get(config('graphqlite.uri'), 'TheCodingMachine\\GraphQLite\\Laravel\\Controllers\\GraphQLiteController@index');
-Route::post(config('graphqlite.uri'), 'TheCodingMachine\\GraphQLite\\Laravel\\Controllers\\GraphQLiteController@index');
+Route::get(config('graphqlite.uri', '/graphql'), 'TheCodingMachine\\GraphQLite\\Laravel\\Controllers\\GraphQLiteController@index');
+Route::post(config('graphqlite.uri', '/graphql'), 'TheCodingMachine\\GraphQLite\\Laravel\\Controllers\\GraphQLiteController@index');