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/tapable/lib/util-browser.js

@@ -0,0 +1,16 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+"use strict";
+
+exports.deprecate = (fn, msg) => {
+	let once = true;
+	return function () {
+		if (once) {
+			console.warn("DeprecationWarning: " + msg);
+			once = false;
+		}
+		return fn.apply(this, arguments);
+	};
+};