Enable JSON output for search functionality

Add JSON output format to home page outputs to generate the search index
required by hugo-book theme's flexsearch feature.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: DavidLiedle

website/hugo.yaml

@@ -59,6 +59,12 @@ menu:
       url: "https://iolanguage.org"
       weight: 20
 
+outputs:
+  home:
+    - HTML
+    - RSS
+    - JSON
+
 markup:
   goldmark:
     renderer: