Is there Ghost theme like this one?

Is there a ghost Theme that’s similar to this Theme on Github IO? Understanding the Neural Tangent Kernel – Rajat's Blog – A blog about machine learning and math.

I like that it

  1. Doesn’t have unnecessary whitespace when viewing on wide monitors
  2. Supports collapsible sections (click to expand)

I’m not sure on something like that theme.
I would note though, the editor has /toggle. This will let you create a collapsible section, the downside is, as far as I can tell, it only allows standard text.