Cool but why not just use regular MD with YAML front matter? I don't find that JSON readable at all, comparatively, and that INI isn't any better than the YAML version.

   ---
   includes: docs/index.html.md menu menuTop
   title: Theme
   base: docs/docs.html
   slug: theme
   menu:
    - label: Demo
      url: /demo/features
    - label: Try it!
      url: /try.html?d=/data/try.json
    - label: Docs
      url: /doc
   ---
   
   # Customize the story
   
   Below are the parameters to customize the style of the story.

And… PHP in a MD file?