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/@jest/reporters/build/generateEmptyCoverage.d.ts

@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+import type { V8Coverage } from 'collect-v8-coverage';
+import { FileCoverage } from 'istanbul-lib-coverage';
+import type { Config } from '@jest/types';
+declare type SingleV8Coverage = V8Coverage[number];
+export declare type CoverageWorkerResult = {
+    kind: 'BabelCoverage';
+    coverage: FileCoverage;
+} | {
+    kind: 'V8Coverage';
+    result: SingleV8Coverage;
+};
+export default function generateEmptyCoverage(source: string, filename: Config.Path, globalConfig: Config.GlobalConfig, config: Config.ProjectConfig, changedFiles?: Set<Config.Path>, sourcesRelatedToTestsInChangedFiles?: Set<Config.Path>): Promise<CoverageWorkerResult | null>;
+export {};