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/@babel/runtime/helpers/inherits.js

@@ -0,0 +1,14 @@
+var setPrototypeOf = require("./setPrototypeOf.js");
+function _inherits(t, e) {
+  if ("function" != typeof e && null !== e) throw new TypeError("Super expression must either be null or a function");
+  t.prototype = Object.create(e && e.prototype, {
+    constructor: {
+      value: t,
+      writable: !0,
+      configurable: !0
+    }
+  }), Object.defineProperty(t, "prototype", {
+    writable: !1
+  }), e && setPrototypeOf(t, e);
+}
+module.exports = _inherits, module.exports.__esModule = true, module.exports["default"] = module.exports;