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/import-fresh/index.d.ts

@@ -0,0 +1,30 @@
+/**
+Import a module while bypassing the cache.
+
+@example
+```
+// foo.js
+let i = 0;
+module.exports = () => ++i;
+
+// index.js
+import importFresh = require('import-fresh');
+
+require('./foo')();
+//=> 1
+
+require('./foo')();
+//=> 2
+
+importFresh('./foo')();
+//=> 1
+
+importFresh('./foo')();
+//=> 1
+
+const foo = importFresh<typeof import('./foo')>('./foo');
+```
+*/
+declare function importFresh<T>(moduleId: string): T;
+
+export = importFresh;