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/string-trim-start.js

@@ -0,0 +1,11 @@
+'use strict';
+var $trimStart = require('../internals/string-trim').start;
+var forcedStringTrimMethod = require('../internals/string-trim-forced');
+
+// `String.prototype.{ trimStart, trimLeft }` method
+// https://tc39.es/ecma262/#sec-string.prototype.trimstart
+// https://tc39.es/ecma262/#String.prototype.trimleft
+module.exports = forcedStringTrimMethod('trimStart') ? function trimStart() {
+  return $trimStart(this);
+// eslint-disable-next-line es/no-string-prototype-trimstart-trimend -- safe
+} : ''.trimStart;