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/find.js

@@ -0,0 +1,10 @@
+import isArrayLike from './_isArrayLike.js';
+import findIndex from './findIndex.js';
+import findKey from './findKey.js';
+
+// Return the first value which passes a truth test.
+export default function find(obj, predicate, context) {
+  var keyFinder = isArrayLike(obj) ? findIndex : findKey;
+  var key = keyFinder(obj, predicate, context);
+  if (key !== void 0 && key !== -1) return obj[key];
+}