chore: Add treemap example

packages/examples/src/examples/treemap.ts

@@ -0,0 +1,21 @@
+import type { DiagramMetadata } from '../types.js';
+
+export default {
+  id: 'treemap',
+  name: 'Treemap',
+  description: 'Visualize hierarchical data as nested rectangles',
+  examples: [
+    {
+      title: 'Treemap',
+      isDefault: true,
+      code: `treemap-beta
+"Section 1"
+    "Leaf 1.1": 12
+    "Section 1.2"
+      "Leaf 1.2.1": 12
+"Section 2"
+    "Leaf 2.1": 20
+    "Leaf 2.2": 25`,
+    },
+  ],
+} satisfies DiagramMetadata;