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/underscore/cjs/_toBufferView.js

@@ -0,0 +1,13 @@
+var _getByteLength = require('./_getByteLength.js');
+
+// Internal function to wrap or shallow-copy an ArrayBuffer,
+// typed array or DataView to a new view, reusing the buffer.
+function toBufferView(bufferSource) {
+  return new Uint8Array(
+    bufferSource.buffer || bufferSource,
+    bufferSource.byteOffset || 0,
+    _getByteLength(bufferSource)
+  );
+}
+
+module.exports = toBufferView;