Implements the library and cient actions to use DOMPurify.

Library's short discription:

DOMPurify is a DOM-only, super-fast, uber-tolerant XSS sanitizer for HTML, MathML and SVG.

DOMPurify is written in JavaScript and works in all modern browsers (Safari (10+), Opera (15+), Edge, Firefox and Chrome - as well as almost anything else using Blink, Gecko or WebKit). It doesn't break on MSIE or other legacy browsers. It simply does nothing.