Which elements support shadow DOM?
Oliver on twitter asked: Is there a list somewhere of which HTML elements can and can’t have a shadow DOM? As it turns out, there is! (Big thanks to Anne van Kesteren for showing us the way). If context object’s local name is not a valid custom element name, article, aside, blockquote, body, div, footer, h1, h2, h3, h4, h5, h6, header, main, nav, p, section, or span, then throw a NotSupportedError DOMException.