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/unique-string/index.d.ts

@@ -0,0 +1,16 @@
+/**
+Generate a unique random string.
+
+@returns A 32 character unique string. Matches the length of MD5, which is [unique enough](https://stackoverflow.com/a/2444336/64949) for non-crypto purposes.
+
+@example
+```
+import uniqueString = require('unique-string');
+
+uniqueString();
+//=> 'b4de2a49c8ffa3fbee04446f045483b2'
+```
+*/
+declare function uniqueString(): string;
+
+export = uniqueString;