Resolve "Enforce user authorization"

To make a page check if user is logged in, it has to load the ./js/authorization.js file.

Closes #13 (closed)

public/js/app.js

-// Obtener referencia a los elementos del DOM
+// Get reference to DOM elements
 const taskList = document.querySelector('.task-list ul');
 const newTaskForm = document.querySelector('form');