Need Documentation/references for creating a custom Swagger UI theme/layout

Hi, 

I have a requirement for implementing API References using swagger json files ( swagger UI) showcased through a custom layout, I'm trying to go through the official documentation but it doesn't give much context on how to go ahead and create our own theme or preset, instead of the default layout. Can anyone guide me with steps or sample github repo for customising swagger UI?

Attaching a screenshot on how the UI should look like, any guidance on the implementation steps will be greatly helpful. We currently use HUGO for our documentation site and can either implement api references as part of the markdown content or as a separate UI layout.. 

Thanks in advance!