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-pure/modules/es.promise.with-resolvers.js

@@ -0,0 +1,16 @@
+'use strict';
+var $ = require('../internals/export');
+var newPromiseCapabilityModule = require('../internals/new-promise-capability');
+
+// `Promise.withResolvers` method
+// https://tc39.es/ecma262/#sec-promise.withResolvers
+$({ target: 'Promise', stat: true }, {
+  withResolvers: function withResolvers() {
+    var promiseCapability = newPromiseCapabilityModule.f(this);
+    return {
+      promise: promiseCapability.promise,
+      resolve: promiseCapability.resolve,
+      reject: promiseCapability.reject
+    };
+  }
+});