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/regexp-unsupported-dot-all.js

@@ -0,0 +1,11 @@
+'use strict';
+var fails = require('../internals/fails');
+var globalThis = require('../internals/global-this');
+
+// babel-minify and Closure Compiler transpiles RegExp('.', 's') -> /./s and it causes SyntaxError
+var $RegExp = globalThis.RegExp;
+
+module.exports = fails(function () {
+  var re = $RegExp('.', 's');
+  return !(re.dotAll && re.test('\n') && re.flags === 's');
+});