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.test.js

@@ -0,0 +1,20 @@
+"use strict";
+
+var assert = require("@sinonjs/referee-sinon").assert;
+var valueToString = require("./value-to-string");
+
+describe("util/core/valueToString", function () {
+    it("returns string representation of an object", function () {
+        var obj = {};
+
+        assert.equals(valueToString(obj), obj.toString());
+    });
+
+    it("returns 'null' for literal null'", function () {
+        assert.equals(valueToString(null), "null");
+    });
+
+    it("returns 'undefined' for literal undefined", function () {
+        assert.equals(valueToString(undefined), "undefined");
+    });
+});