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/to-length.js

@@ -0,0 +1,11 @@
+'use strict';
+var toIntegerOrInfinity = require('../internals/to-integer-or-infinity');
+
+var min = Math.min;
+
+// `ToLength` abstract operation
+// https://tc39.es/ecma262/#sec-tolength
+module.exports = function (argument) {
+  var len = toIntegerOrInfinity(argument);
+  return len > 0 ? min(len, 0x1FFFFFFFFFFFFF) : 0; // 2 ** 53 - 1 == 9007199254740991
+};