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.math.expm1.js

@@ -0,0 +1,8 @@
+'use strict';
+var $ = require('../internals/export');
+var expm1 = require('../internals/math-expm1');
+
+// `Math.expm1` method
+// https://tc39.es/ecma262/#sec-math.expm1
+// eslint-disable-next-line es/no-math-expm1 -- required for testing
+$({ target: 'Math', stat: true, forced: expm1 !== Math.expm1 }, { expm1: expm1 });