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.f16round.js

@@ -0,0 +1,15 @@
+'use strict';
+var $ = require('../internals/export');
+var floatRound = require('../internals/math-float-round');
+
+var FLOAT16_EPSILON = 0.0009765625;
+var FLOAT16_MAX_VALUE = 65504;
+var FLOAT16_MIN_VALUE = 6.103515625e-05;
+
+// `Math.f16round` method
+// https://tc39.es/ecma262/#sec-math.f16round
+$({ target: 'Math', stat: true }, {
+  f16round: function f16round(x) {
+    return floatRound(x, FLOAT16_EPSILON, FLOAT16_MAX_VALUE, FLOAT16_MIN_VALUE);
+  }
+});