merge master and improvements

public/sw.js

@@ -1,8 +1,6 @@
 // Notification click event listener
 self.addEventListener("notificationclick", (e) => {
-  // Close the notification popout
   e.notification.close();
-  // Get all the Window clients
   e.waitUntil(
     clients.matchAll({ type: "window" }).then((clientsArr) => {
       // If a Window tab matching the targeted URL already exists, focus that;
@@ -26,9 +24,10 @@ async function checkNewMessages() {
   // Todo...
 }
 
+// Install PWA in mobile or web to test if periodicSync notification works
+// see browser compatibility: https://developer.mozilla.org/en-US/docs/Web/API/Web_Periodic_Background_Synchronization_API#browser_compatibility
 self.addEventListener('periodicsync', (event) => {
   if (event.tag === 'check-new-messages') {
-    // Test if periodicSync notification triggers in Mobile app(created via add to homescreen)
     self.registration.showNotification("Notification via periodicSync");
 
     event.waitUntil(checkNewMessages());