Lägger till service worker och uppdaterar manifest.json för att stödja PWA

public/app.js

@@ -1,3 +1,15 @@
+if ('serviceWorker' in navigator) {
+    window.addEventListener('load', () => {
+        navigator.serviceWorker.register('/service-worker.js')
+            .then(registration => {
+                console.log('ServiceWorker registration successful with scope: ', registration.scope);
+            })
+            .catch(error => {
+                console.log('ServiceWorker registration failed: ', error);
+            });
+    });
+}
+
 document.getElementById('taskForm').addEventListener('submit', function(e) {
     e.preventDefault();