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/modules/omit.js

@@ -0,0 +1,22 @@
+import restArguments from './restArguments.js';
+import isFunction from './isFunction.js';
+import negate from './negate.js';
+import map from './map.js';
+import flatten from './_flatten.js';
+import contains from './contains.js';
+import pick from './pick.js';
+
+// Return a copy of the object without the disallowed properties.
+export default restArguments(function(obj, keys) {
+  var iteratee = keys[0], context;
+  if (isFunction(iteratee)) {
+    iteratee = negate(iteratee);
+    if (keys.length > 1) context = keys[1];
+  } else {
+    keys = map(flatten(keys, false, false), String);
+    iteratee = function(value, key) {
+      return !contains(keys, key);
+    };
+  }
+  return pick(obj, iteratee, context);
+});