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/rpc-ipc/error/RpcIpcMessagePortClosedError.d.ts

@@ -0,0 +1,7 @@
+import { RpcMessagePortClosedError } from '../../error/RpcMessagePortClosedError';
+declare class RpcIpcMessagePortClosedError extends RpcMessagePortClosedError {
+    readonly code?: string | number | null | undefined;
+    readonly signal?: string | null | undefined;
+    constructor(message: string, code?: string | number | null | undefined, signal?: string | null | undefined);
+}
+export { RpcIpcMessagePortClosedError };

node_modules/fork-ts-checker-webpack-plugin/lib/rpc/rpc-ipc/error/RpcIpcMessagePortClosedError.js

@@ -0,0 +1,12 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const RpcMessagePortClosedError_1 = require("../../error/RpcMessagePortClosedError");
+class RpcIpcMessagePortClosedError extends RpcMessagePortClosedError_1.RpcMessagePortClosedError {
+    constructor(message, code, signal) {
+        super(message);
+        this.code = code;
+        this.signal = signal;
+        this.name = 'RpcIpcMessagePortClosedError';
+    }
+}
+exports.RpcIpcMessagePortClosedError = RpcIpcMessagePortClosedError;