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/global.test.js

@@ -0,0 +1,16 @@
+"use strict";
+
+var assert = require("@sinonjs/referee-sinon").assert;
+var globalObject = require("./global");
+
+describe("global", function () {
+    before(function () {
+        if (typeof global === "undefined") {
+            this.skip();
+        }
+    });
+
+    it("is same as global", function () {
+        assert.same(globalObject, global);
+    });
+});