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/esnext.array.unique-by.js

@@ -0,0 +1,12 @@
+'use strict';
+var $ = require('../internals/export');
+var addToUnscopables = require('../internals/add-to-unscopables');
+var uniqueBy = require('../internals/array-unique-by');
+
+// `Array.prototype.uniqueBy` method
+// https://github.com/tc39/proposal-array-unique
+$({ target: 'Array', proto: true, forced: true }, {
+  uniqueBy: uniqueBy
+});
+
+addToUnscopables('uniqueBy');