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.string.trim.js

@@ -0,0 +1,12 @@
+'use strict';
+var $ = require('../internals/export');
+var $trim = require('../internals/string-trim').trim;
+var forcedStringTrimMethod = require('../internals/string-trim-forced');
+
+// `String.prototype.trim` method
+// https://tc39.es/ecma262/#sec-string.prototype.trim
+$({ target: 'String', proto: true, forced: forcedStringTrimMethod('trim') }, {
+  trim: function trim() {
+    return $trim(this);
+  }
+});