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/whatwg-url/dist/encoding.js

@@ -0,0 +1,26 @@
+"use strict";
+let { TextEncoder, TextDecoder } = require("util");
+// Handle browserify's lack of support (https://github.com/browserify/node-util/issues/46), which
+// is important for the live viewer:
+if (!TextEncoder) {
+  TextEncoder = global.TextEncoder;
+}
+if (!TextDecoder) {
+  TextDecoder = global.TextDecoder;
+}
+
+const utf8Encoder = new TextEncoder();
+const utf8Decoder = new TextDecoder("utf-8", { ignoreBOM: true });
+
+function utf8Encode(string) {
+  return utf8Encoder.encode(string);
+}
+
+function utf8DecodeWithoutBOM(bytes) {
+  return utf8Decoder.decode(bytes);
+}
+
+module.exports = {
+  utf8Encode,
+  utf8DecodeWithoutBOM
+};