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/helpers/defaultEndianness.js

@@ -0,0 +1,21 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $Uint8Array = GetIntrinsic('%Uint8Array%', true);
+var $Uint32Array = GetIntrinsic('%Uint32Array%', true);
+
+var typedArrayBuffer = require('typed-array-buffer');
+
+var uInt32 = $Uint32Array && new $Uint32Array([0x12345678]);
+var uInt8 = uInt32 && new $Uint8Array(typedArrayBuffer(uInt32));
+
+module.exports = uInt8
+	? uInt8[0] === 0x78
+		? 'little'
+		: uInt8[0] === 0x12
+			? 'big'
+			: uInt8[0] === 0x34
+				? 'mixed' // https://developer.mozilla.org/en-US/docs/Glossary/Endianness
+				: 'unknown' // ???
+	: 'indeterminate'; // no way to know