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-core/registerQuotaErrorCallback.d.ts

@@ -0,0 +1,10 @@
+import './_version.js';
+/**
+ * Adds a function to the set of quotaErrorCallbacks that will be executed if
+ * there's a quota error.
+ *
+ * @param {Function} callback
+ * @memberof workbox-core
+ */
+declare function registerQuotaErrorCallback(callback: Function): void;
+export { registerQuotaErrorCallback };