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/isDataView.js

@@ -0,0 +1,16 @@
+var _tagTester = require('./_tagTester.js');
+var isFunction = require('./isFunction.js');
+var _stringTagBug = require('./_stringTagBug.js');
+var isArrayBuffer = require('./isArrayBuffer.js');
+
+var isDataView = _tagTester('DataView');
+
+// In IE 10 - Edge 13, we need a different heuristic
+// to determine whether an object is a `DataView`.
+function ie10IsDataView(obj) {
+  return obj != null && isFunction(obj.getInt8) && isArrayBuffer(obj.buffer);
+}
+
+var isDataView$1 = (_stringTagBug.hasStringTagBug ? ie10IsDataView : isDataView);
+
+module.exports = isDataView$1;