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/harmony-reflect/index.d.ts

@@ -0,0 +1,20 @@
+declare type PropertyKey = string | number | symbol;
+
+declare namespace Reflect {
+    function apply(target: Function, thisArgument: any, argumentsList: ArrayLike<any>): any;
+    function construct(target: Function, argumentsList: ArrayLike<any>, newTarget?: any): any;
+    function defineProperty(target: any, propertyKey: PropertyKey, attributes: PropertyDescriptor): boolean;
+    function deleteProperty(target: any, propertyKey: PropertyKey): boolean;
+    function get(target: any, propertyKey: PropertyKey, receiver?: any): any;
+    function getOwnPropertyDescriptor(target: any, propertyKey: PropertyKey): PropertyDescriptor;
+    function getPrototypeOf(target: any): any;
+    function has(target: any, propertyKey: string): boolean;
+    function has(target: any, propertyKey: symbol): boolean;
+    function isExtensible(target: any): boolean;
+    function ownKeys(target: any): Array<PropertyKey>;
+    function preventExtensions(target: any): boolean;
+    function set(target: any, propertyKey: PropertyKey, value: any, receiver?: any): boolean;
+    function setPrototypeOf(target: any, proto: any): boolean;
+}
+
+export = Reflect;