Introduce "AppSession"

src/base/AppSession.ts

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) Contributors to the Suwayomi project
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+import { BrowserUtil } from '@/lib/BrowserUtil.ts';
+import { AppStorage } from '@/lib/storage/AppStorage.ts';
+
+const STARTUP_TIMESTAMP_KEY = 'webUIStartupTimestamp';
+
+class AppSessionClass {
+    constructor() {
+        if (BrowserUtil.isActualPageLoad()) {
+            AppStorage.session.setItem(STARTUP_TIMESTAMP_KEY, Date.now());
+        }
+    }
+
+    get STARTUP_TIMESTAMP(): number {
+        return AppStorage.session.getItemParsed(STARTUP_TIMESTAMP_KEY, Date.now());
+    }
+}
+
+export const AppSession = new AppSessionClass();