Update the documentation to show the internal StoryInterface passage

[BawdyInkSlinger]

Is your feature request related to a problem? I want to take the body of my passage and wrap it in a main HTML element. I'm already using PassageHeader, and I DON'T want its content wrapped in the main element. This way, I can easily refer to $("main") when I need to refer to the passage body. Right now, I have to refer to everything that's not the header, but at the same depth. Pretty inconvenient.

Describe the solution you'd like. After browsing the documentation, it seems like the easiest way of doing this would be to create my own StoryInterface passage. But, I just want to modify one piece of it, not rewrite it from scratch. Unfortunately, the HTML example example is full of ....

Wouldn't it be possible to fill those in with the content that SugarCube really uses for its default StoryInterface? That way, I could just copy and paste that file and modify this one thing.

I know the documentation says that the ... is for dynamic content, but that doesn't give me enough context to understand why this can't be done; a custom StoryInterface can have dynamic content too.

Describe alternatives you've considered. I think there is a :storystart solution here.