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/RpcService.d.ts

@@ -0,0 +1,12 @@
+import { RpcProcedure } from './RpcProcedure';
+import { RpcMessagePort } from './RpcMessagePort';
+declare type RpcCallHandler<TPayload = any, TResult = any> = (payload: TPayload) => Promise<TResult>;
+interface RpcService {
+    readonly isOpen: () => boolean;
+    readonly open: () => Promise<void>;
+    readonly close: () => Promise<void>;
+    readonly addCallHandler: <TPayload, TResult>(procedure: RpcProcedure<TPayload, TResult>, handler: RpcCallHandler<TPayload, TResult>) => void;
+    readonly removeCallHandler: <TPayload, TResult>(procedure: RpcProcedure<TPayload, TResult>) => void;
+}
+declare function createRpcService(port: RpcMessagePort): RpcService;
+export { RpcService, createRpcService };