fn = () => {
  return {
    doctype: {
      enter: (node, parentNode) => {
        detachNodeFromParent(node, parentNode);
      },
    },
  };
}
Remove DOCTYPE declaration.

"Unfortunately the SVG DTDs are a source of so many
issues that the SVG WG has decided not to write one
for the upcoming SVG 1.2 standard. In fact SVG WG
members are even telling people not to use a DOCTYPE
declaration in SVG 1.0 and 1.1 documents"
https://jwatt.org/svg/authoring/#doctype-declaration

@example
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
q"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

@example
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" [
    <!-- an internal subset can be embedded here -->
]>

@author Kir Belevich

@type {import('../lib/types.js').Plugin}