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/escalade/index.d.mts

@@ -0,0 +1,11 @@
+type Promisable<T> = T | Promise<T>;
+
+export type Callback = (
+	directory: string,
+	files: string[],
+) => Promisable<string | false | void>;
+
+export default function (
+	directory: string,
+	callback: Callback,
+): Promise<string | void>;