confirm dialog on close or refresh page

src/app/app.component.ts

-import { ChangeDetectorRef, Component, ElementRef, ViewChild } from '@angular/core';
+import { ChangeDetectorRef, Component, ElementRef, HostListener, ViewChild } from '@angular/core';
 import { Mission } from './class/mission/mission';
 import { Scenario } from './class/scenario/scenario';
 import { Step } from './class/step/step';
@@ -46,6 +46,13 @@ export class AppComponent {
     });
   }
 
+  @HostListener('window:beforeunload', ['$event'])
+  beforeUnloadHandler(event: any) {
+    const message = "Êtes vous sûr de vouloir quitter RLG Maker ?\nVous risquez de perdre les données non sauvegardées.";
+    event.returnValue = message;
+    return message;
+  }
+
   downloadFile(): void {
     const jsonString = JSON.stringify(this.scenario);
     const blob = new Blob([jsonString], { type: 'application/json' });