Try new saving technique for PWA

src/WindowBehavior.ts

@@ -16,21 +16,7 @@ const handleResize = (canvas: HTMLCanvasElement) => {
   }
 };
 
-export const installWindowBehaviors = (
+const saveBeforeExit = (app: Editor): void => {
-  app: Editor,
-  window: Window,
-  preventMultipleTabs: boolean = false
-) => {
-
-
-
-  window.addEventListener("resize", () =>
-    handleResize(app.interface.scope as HTMLCanvasElement)
-  );
-  window.addEventListener("resize", () =>
-    handleResize(app.interface.feedback as HTMLCanvasElement)
-  );
-  window.addEventListener("beforeunload", () => {
   // @ts-ignore
   event.preventDefault();
   // Iterate over all local files and set the candidate to the committed
@@ -39,6 +25,25 @@ export const installWindowBehaviors = (
   app.settings.saveApplicationToLocalStorage(app.universes, app.settings);
   app.clock.stop();
   return null;
+};
+
+export const installWindowBehaviors = (
+  app: Editor,
+  window: Window,
+  preventMultipleTabs: boolean = false
+) => {
+
+  window.addEventListener("resize", () =>
+    handleResize(app.interface.scope as HTMLCanvasElement)
+  );
+  window.addEventListener("resize", () =>
+    handleResize(app.interface.feedback as HTMLCanvasElement)
+  );
+  window.addEventListener("beforeunload", () => {
+    saveBeforeExit(app)
+  });
+  window.addEventListener("visibilitychange", () => {
+    saveBeforeExit(app)
   });
 
   if (preventMultipleTabs) {