I like this. The nice thing about the Scroll implementation is that it's designed with extensibility in mind. I expect one day someone builds a `sidenotes` keyw

I like this. The nice thing about the Scroll implementation is that it's designed with extensibility in mind. I expect one day someone builds a `sidenotes` keyword. I think the colors idea is good too. Some stuff for us to play with in the future. Thanks for sharing!