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/map-helpers.js

@@ -0,0 +1,15 @@
+'use strict';
+var uncurryThis = require('../internals/function-uncurry-this');
+
+// eslint-disable-next-line es/no-map -- safe
+var MapPrototype = Map.prototype;
+
+module.exports = {
+  // eslint-disable-next-line es/no-map -- safe
+  Map: Map,
+  set: uncurryThis(MapPrototype.set),
+  get: uncurryThis(MapPrototype.get),
+  has: uncurryThis(MapPrototype.has),
+  remove: uncurryThis(MapPrototype['delete']),
+  proto: MapPrototype
+};