Consider defining `Node` as a union type that includes collections, and getting rid of `Text` and `Fragment`

[davepeck]

For developers familiar with typing in the React world, React.ReactNode can be both a singleton or a collection. We should consider doing the same:

type Node = Element | Comment | DocumentType | str | Iterable[Node]

Now that we build on top of MarkupSafe, Text serves less of a purpose. We could get rid of it in favor of just “str”, probably. Likewise, Fragment is basically an Iterable[Node].

The benefit is simpler typing for developers: in components, for example, they can type children as Node rather than Iterable[Node].

The drawback is that you can't just str(some_node) to render it anymore; you'd need to call a new top-level tdom.render() method.

I don't know which is preferable overall.