[dom] Use `commonAncestorContainer` in concept-range-clone (#56)

https://dom.spec.whatwg.org/#concept-range-clone

> * 4. Let common ancestor be original start node.
> * 5. While common ancestor is not an inclusive ancestor of original end node, set common ancestor to its own parent. 

This is *range*'s `commonAncestorContainer`.

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https://github.com/whatwg/dom/issues/56