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-routing/utils/normalizeHandler.d.ts

@@ -0,0 +1,10 @@
+import { RouteHandler, RouteHandlerObject } from 'workbox-core/types.js';
+import '../_version.js';
+/**
+ * @param {function()|Object} handler Either a function, or an object with a
+ * 'handle' method.
+ * @return {Object} An object with a handle method.
+ *
+ * @private
+ */
+export declare const normalizeHandler: (handler: RouteHandler) => RouteHandlerObject;