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/globalthis/shim.js

@@ -0,0 +1,29 @@
+'use strict';
+
+var define = require('define-properties');
+var gOPD = require('gopd');
+var getPolyfill = require('./polyfill');
+
+module.exports = function shimGlobal() {
+	var polyfill = getPolyfill();
+	if (define.supportsDescriptors) {
+		var descriptor = gOPD(polyfill, 'globalThis');
+		if (
+			!descriptor
+			|| (
+				descriptor.configurable
+				&& (descriptor.enumerable || !descriptor.writable || globalThis !== polyfill)
+			)
+		) {
+			Object.defineProperty(polyfill, 'globalThis', {
+				configurable: true,
+				enumerable: false,
+				value: polyfill,
+				writable: true
+			});
+		}
+	} else if (typeof globalThis !== 'object' || globalThis !== polyfill) {
+		polyfill.globalThis = polyfill;
+	}
+	return polyfill;
+};