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/style-loader/dist/runtime/insertStyleElement.js

@@ -0,0 +1,10 @@
+"use strict";
+
+/* istanbul ignore next  */
+function insertStyleElement(options) {
+  var element = document.createElement("style");
+  options.setAttributes(element, options.attributes);
+  options.insert(element, options.options);
+  return element;
+}
+module.exports = insertStyleElement;