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/es-abstract/2020/StrictEqualityComparison.js

@@ -0,0 +1,15 @@
+'use strict';
+
+var Type = require('./Type');
+
+// https://262.ecma-international.org/5.1/#sec-11.9.6
+
+module.exports = function StrictEqualityComparison(x, y) {
+	if (Type(x) !== Type(y)) {
+		return false;
+	}
+	if (typeof x === 'undefined' || x === null) {
+		return true;
+	}
+	return x === y; // shortcut for steps 4-7
+};