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/modules/es.parse-float.js

@@ -0,0 +1,9 @@
+'use strict';
+var $ = require('../internals/export');
+var $parseFloat = require('../internals/number-parse-float');
+
+// `parseFloat` method
+// https://tc39.es/ecma262/#sec-parsefloat-string
+$({ global: true, forced: parseFloat !== $parseFloat }, {
+  parseFloat: $parseFloat
+});