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/source-map/lib/base64.js

@@ -0,0 +1,19 @@
+/* -*- Mode: js; js-indent-level: 2; -*- */
+/*
+ * Copyright 2011 Mozilla Foundation and contributors
+ * Licensed under the New BSD license. See LICENSE or:
+ * http://opensource.org/licenses/BSD-3-Clause
+ */
+
+const intToCharMap =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".split("");
+
+/**
+ * Encode an integer in the range of 0 to 63 to a single base 64 digit.
+ */
+exports.encode = function (number) {
+  if (0 <= number && number < intToCharMap.length) {
+    return intToCharMap[number];
+  }
+  throw new TypeError("Must be between 0 and 63: " + number);
+};