LibWeb: Parse SVG document types as XML documents
We began parsing SVG documents as HTML years ago in commit 05be648. This
was long before we had an XML parser, and actually violates the spec.
Since SVG documents have a MIME type of "image/svg+xml", the spec
mandates the document should be parsed as XML.
One impact here is that the SVG document is no longer "fixed" to include
<html>, <head>, and <body> tags. This will have prevented document.title
from detecting the document element is an SVG element.
Timothy Flynn