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/postcss-image-set-function/dist/lib/process-image-set.d.ts

@@ -0,0 +1,14 @@
+import type { Declaration, Result, Postcss } from 'postcss';
+import type { Node } from 'postcss-value-parser';
+declare type imageSetFunction = {
+    imageSetFunction: Node;
+    imageSetOptionNodes: Array<Node>;
+};
+export declare const processImageSet: (imageSetFunctions: Array<imageSetFunction>, decl: Declaration, opts: {
+    decl: Declaration;
+    oninvalid: string;
+    preserve: boolean;
+    result: Result;
+    postcss: Postcss;
+}) => void;
+export {};