Initial commit: Developer Tools MVP with visual editor

- Complete React app with 7 developer tools
- JSON Tool with visual structured editor
- Serialize Tool with visual structured editor
- URL, Base64, CSV/JSON, Beautifier, Diff tools
- Responsive navigation with dropdown menu
- Dark/light mode toggle
- Mobile-responsive design with sticky header
- All tools working with copy/paste functionality

node_modules/workbox-background-sync/index.d.ts

@@ -0,0 +1,25 @@
+import { BackgroundSyncPlugin } from './BackgroundSyncPlugin.js';
+import { Queue, QueueOptions } from './Queue.js';
+import { QueueStore } from './QueueStore.js';
+import { StorableRequest } from './StorableRequest.js';
+import './_version.js';
+interface SyncManager {
+    getTags(): Promise<string[]>;
+    register(tag: string): Promise<void>;
+}
+declare global {
+    interface ServiceWorkerRegistration {
+        readonly sync: SyncManager;
+    }
+    interface SyncEvent extends ExtendableEvent {
+        readonly lastChance: boolean;
+        readonly tag: string;
+    }
+    interface ServiceWorkerGlobalScopeEventMap {
+        sync: SyncEvent;
+    }
+}
+/**
+ * @module workbox-background-sync
+ */
+export { BackgroundSyncPlugin, Queue, QueueOptions, QueueStore, StorableRequest };