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/internals/function-apply.js

@@ -0,0 +1,11 @@
+'use strict';
+var NATIVE_BIND = require('../internals/function-bind-native');
+
+var FunctionPrototype = Function.prototype;
+var apply = FunctionPrototype.apply;
+var call = FunctionPrototype.call;
+
+// eslint-disable-next-line es/no-function-prototype-bind, es/no-reflect -- safe
+module.exports = typeof Reflect == 'object' && Reflect.apply || (NATIVE_BIND ? call.bind(apply) : function () {
+  return call.apply(apply, arguments);
+});