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/core-js/es/promise/with-resolvers.js

@@ -0,0 +1,13 @@
+'use strict';
+require('../../modules/es.promise');
+require('../../modules/es.promise.with-resolvers');
+var call = require('../../internals/function-call');
+var isCallable = require('../../internals/is-callable');
+var path = require('../../internals/path');
+
+var Promise = path.Promise;
+var promiseWithResolvers = Promise.withResolvers;
+
+module.exports = function withResolvers() {
+  return call(promiseWithResolvers, isCallable(this) ? this : Promise);
+};