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/amd/isDataView.js

@@ -0,0 +1,15 @@
+define(['./_tagTester', './isFunction', './_stringTagBug', './isArrayBuffer'], function (_tagTester, isFunction, _stringTagBug, isArrayBuffer) {
+
+  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);
+
+  return isDataView$1;
+
+});