Elements can have text children
Add convenience traits to easily convert element child types
Traditional text nodes know their document
Text nodes know their parents
Text can be changed
Elements can have comment children
DRY up delegation of Show and PartialEq to rdom
Traditional comments know their document
Comments know their parents
Comments can be changed
Elements can have processing instruction children
Traditional processing instructions know their document
Processing instructions can be changed
Traditional root node knows its document
The root can have element children
The root can have comment children
The root can have processing instruction children
The root node only holds one element
Processing instructions know their parents
Elements under the root know their parents