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/fork-ts-checker-webpack-plugin/lib/rpc/RpcMessageChannel.d.ts

@@ -0,0 +1,10 @@
+import { RpcMessagePort } from './RpcMessagePort';
+interface RpcMessageChannel {
+    readonly servicePort: RpcMessagePort;
+    readonly clientPort: RpcMessagePort;
+    readonly isOpen: () => boolean;
+    readonly open: () => Promise<void>;
+    readonly close: () => Promise<void>;
+}
+declare function createRpcMessageChannel(servicePort: RpcMessagePort, clientPort: RpcMessagePort, linkPorts?: () => Promise<void>, unlinkPorts?: () => Promise<void>): RpcMessageChannel;
+export { RpcMessageChannel, createRpcMessageChannel };