Add update notification

ngsw-config.json

@@ -17,6 +17,7 @@
     {
       "name": "app",
       "installMode": "prefetch",
+      "updateMode": "prefetch",
       "resources": {
         "files": [
           "/favicon.ico",

src/app/app.component.ts

-import { Component } from '@angular/core';
+import { Component, OnInit } from '@angular/core';
 import { TranslateService } from '@ngx-translate/core';
-import { ThemeService } from '../theme/theme.service';
+import { SwUpdate } from '@angular/service-worker';
+import { NotificationService } from './services/util/notification.service';
 
 @Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.scss']
 })
-export class AppComponent {
+export class AppComponent implements OnInit {
 
   constructor(private translationService: TranslateService,
-              private themeService: ThemeService) {
-
+              private update: SwUpdate,
+              public notification: NotificationService) {
     translationService.setDefaultLang(this.translationService.getBrowserLang());
     sessionStorage.setItem('currentLang', this.translationService.getBrowserLang());
   }
 
   title = 'ARSnova';
+
+  ngOnInit(): void {
+    this.update.available.subscribe(update => {
+      let install: string;
+      this.translationService.get('home-page.install').subscribe(msg => {
+        install = msg;
+      });
+      this.translationService.get('home-page.update-available').subscribe(msg => {
+       this.notification.show(msg, install, {
+          duration: 10000
+        });
+      });
+      this.notification.snackRef.afterDismissed().subscribe(info => {
+        if (info.dismissedByAction === true) {
+          window.location.reload();
+        }
+      });
+    });
+  }
 }

src/assets/i18n/home/de.json

@@ -29,7 +29,9 @@
 		"no-empty-name": "Bitte geben Sie einen Namen ein",
 		"created-1": "Session '",
 		"created-2": "' erfolgreich erstellt",
-		"only-numbers": "Eine Session-ID besteht aus Ziffern"
+		"only-numbers": "Eine Session-ID besteht aus Ziffern",
+        "update-available": "Eine neue Version ist verfügbar.",
+        "install": "Installieren"
 	},
 	"login": {
 		"email": "E-mail",

src/assets/i18n/home/en.json

@@ -29,7 +29,9 @@
 		"no-empty-name": "Please enter a name.",
 		"created-1": "Session '",
 		"created-2": "' successfully created",
-		"only-numbers": "A session-ID only contains digits"
+		"only-numbers": "A session-ID only contains digits",
+        "update-available": "A newer version is available.",
+        "install": "Install"
 	},
 	"login": {
 		"email": "E-mail",