DOM 4 deprecating node type for attributes

[njordhov]

The ATTRIBUTE_NODE constant has been deprecated in DOM4. It should no longer be assumed that an attribute has a nodeType.

The changes to the Attribute interface is initially particularly relevant for the Clojurescript implementation of Hickory. It can be accommodated by not recursively mapping over attributes but instead convert attributes in place when building elements.

[njordhov]

Case in point, in JSDom for Nodejs, attributes don't have a nodeType as they don't inherit from the Node interface.

[njordhov]

The fix is to replace the recursive as-hickory in (map as-hickory (as-seq (aget this "attributes"))) to the equivalent of (fn [this] [(utils/lower-case-keyword (aget this "name")) (aget this "value")]). Ditto for as-hiccup.