message: Mark namespace argument optional
diff: @@ -462,7 +462,7 @@ function newCommentNode(comment: string): parse5.CommentNode {
  };
  }
  -function newElement(tagName: string, namespace: string): Node {
  +function newElement(tagName: string, namespace?: string): Node {
  return {
  nodeName: tagName,
  tagName: tagName,
  