With Gatsby's flexibility, you could certainly add blog functionality to this starter. That being said, the gatsby-starter-docs that inspired this is itself based on the gatsby-starter-advanced which has more robust support for a blog out of the box.
Great idea, and something I thought about including out of the box! This would basically be achieved by replicating the code that builds the Docs page, but namespacing it as Tutorials (or whatever else). You could then reuse the <TableOfContents / > component but pass in the Tutorials data instead.