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/internals/number-is-finite.js

@@ -0,0 +1,11 @@
+'use strict';
+var globalThis = require('../internals/global-this');
+
+var globalIsFinite = globalThis.isFinite;
+
+// `Number.isFinite` method
+// https://tc39.es/ecma262/#sec-number.isfinite
+// eslint-disable-next-line es/no-number-isfinite -- safe
+module.exports = Number.isFinite || function isFinite(it) {
+  return typeof it == 'number' && globalIsFinite(it);
+};