add csrf token

fet2020/templates/tasks/index.html

@@ -39,6 +39,7 @@
                         </div>
                     </div>
                     <form action="" method="post" class="grid grid-cols-1 gap-2 sm:gap-4">
+                        {% csrf_token %}
                         <label class="block">
                             <span class="text-gray-700 dark:text-gray-200">Task-Gruppe</span>
                             <select id="id_tasklist" name="tasklist" class="block w-full mt-1 rounded-md border-gray-300 dark:border-none shadow-sm focus:border-none focus:ring focus:ring-blue-200 dark:focus:ring-sky-700 focus:ring-opacity-50">