Further optimized the target_blank hook for MathML
Further optimized the target_blank hook for MathML

ConradIrwin/DOMPurify,togusafish/t-ashula-_-DOMPurify,Joris-van-der-Wel/DOMPurify,neilj/DOMPurify,tdeekens/DOMPurify,Joris-van-der-Wel/DOMPurify,ConradIrwin/DOMPurify,voku/DOMPurify,kwangkim/DOMPurify,togusafish/t-ashula-_-DOMPurify,tdeekens/DOMPurify,neilj/DOMPurify,voku/DOMPurify,Joris-van-der-Wel/DOMPurify,tdeekens/DOMPurify,neilj/DOMPurify,kwangkim/DOMPurify