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/RpcClient.d.ts

@@ -0,0 +1,10 @@
+import { RpcProcedure, RpcProcedurePayload, RpcProcedureResult } from './RpcProcedure';
+import { RpcMessagePort } from './RpcMessagePort';
+interface RpcClient {
+    readonly isConnected: () => boolean;
+    readonly connect: () => Promise<void>;
+    readonly disconnect: () => Promise<void>;
+    readonly dispatchCall: <TProcedure extends RpcProcedure>(procedure: TProcedure, payload: RpcProcedurePayload<TProcedure>) => Promise<RpcProcedureResult<TProcedure>>;
+}
+declare function createRpcClient(port: RpcMessagePort): RpcClient;
+export { RpcClient, createRpcClient };