`Node` is not visible in the docs

[jDomantas]

Currently the module structure has some pieces that look somewhat like this (type parameters and fields removed for brevity):

mod arena_tree {
    pub struct Node;
}

pub mod nodes {
    pub type AstNode = crate::arena_tree::Node;
}

This means that Node gets exported publicly through comrak::nodes::AstNode, but does not have a documentation page itself (because there is no public item that corresponds to it), so you cannot see what functions it has in the docs. This gets even more confusing as calling functions like Node::traverse produces types that are not even mentioned in the docs, not even behind type aliases.