Add structured fields to tutorials

[alexsb]

Most tutorials reference 1-n demo studies, code for the demo studies, and 1-n typedoc files.

We should have YAML fields for these, and embed them somewhere on the side of the tutorial.

For example, for the Vega demo we have:

Live Demo:
https://revisit.dev/study/demo-vega/

Demo Code:
https://github.com/revisit-studies/study/tree/main/public/demo-vega

Typedoc:
https://revisit.dev/docs/typedoc/interfaces/VegaComponentConfig/
https://revisit.dev/docs/typedoc/interfaces/VegaComponentPath/