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/@sinonjs/commons/lib/value-to-string.js

@@ -0,0 +1,17 @@
+"use strict";
+
+/**
+ * Returns a string representation of the value
+ *
+ * @param  {*} value
+ * @returns {string}
+ */
+function valueToString(value) {
+    if (value && value.toString) {
+        // eslint-disable-next-line @sinonjs/no-prototype-methods/no-prototype-methods
+        return value.toString();
+    }
+    return String(value);
+}
+
+module.exports = valueToString;