Adds ai_recipe_generation sample (#2242)

Adding the demo app from my I/O talk. Because AI.

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

---------

Co-authored-by: Brett Morgan <brett.morgan@gmail.com>

ai_recipe_generation/lib/widgets/cross_image_widget.dart

@@ -0,0 +1,41 @@
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/material.dart';
+import 'package:image_picker/image_picker.dart';
+
+class CrossImage extends StatelessWidget {
+  const CrossImage({
+    super.key,
+    required this.file,
+    this.fit = BoxFit.cover,
+    this.height = 100,
+    this.width = 100,
+  });
+
+  final XFile file;
+  final BoxFit fit;
+  final double width;
+  final double height;
+
+  @override
+  Widget build(BuildContext context) {
+    if (kIsWeb) {
+      return Image.network(
+        file.path,
+        fit: fit,
+      );
+    } else {
+      return Image.file(
+        File(file.path),
+        height: height,
+        width: width,
+      );
+    }
+  }
+
+  static DecorationImage decoration(XFile file, {BoxFit fit = BoxFit.cover}) {
+    final image = kIsWeb ? NetworkImage(file.path) : FileImage(File(file.path));
+    return DecorationImage(image: image as ImageProvider, fit: fit);
+  }
+}