> This documentation should explain that maps are ordered by original insertion order.

"Insertion order" isn't meaningful for immutable maps, but I've added a note about ordering.

> This documentation should explain that `nth` returns a pair from a map. And that length($map) returns the number of pairs.
>
> Correction: I see a mention of nth now. But it was pretty subtle, can we call it with some bullet points, and maybe show how maps are iterated in `@each` if only one variable is provided.

I don't think people are going to want to use most list operations other than `length()` and `@each` with maps very often. `length()` doesn't require an understanding of pairs, and `@each` will work fine if they just always use two variables. I don't think it's worth it to call out the specific structure of listified maps any more than it already is.