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/lodash/_toSource.js

@@ -0,0 +1,26 @@
+/** Used for built-in method references. */
+var funcProto = Function.prototype;
+
+/** Used to resolve the decompiled source of functions. */
+var funcToString = funcProto.toString;
+
+/**
+ * Converts `func` to its source code.
+ *
+ * @private
+ * @param {Function} func The function to convert.
+ * @returns {string} Returns the source code.
+ */
+function toSource(func) {
+  if (func != null) {
+    try {
+      return funcToString.call(func);
+    } catch (e) {}
+    try {
+      return (func + '');
+    } catch (e) {}
+  }
+  return '';
+}
+
+module.exports = toSource;