fixed gruntfile problem

Gruntfile.js

@@ -515,11 +515,11 @@ module.exports = function (grunt) {
         },
         concat: {
             js: {
-                src: 'js/fullCalendar/*/main.js',
+                src: 'node_modules/@fullcalendar/*/main.js',
                 dest: 'js/fullCalendar.js'
             },
             css: {
-                src: 'js/fullCalendar/*/main.min.css',
+                src: 'node_modules/@fullcalendar/*/main.min.css',
                 dest: typo3_css + 'fullCalendar.min.css'
             }
         },