dead link for firefox extention

[Akiyamka]

https://addons.mozilla.org/en-US/firefox/addon/monaco-markdown-github-editor/

Oops! We can’t find that page

[hediet]

Yep, they disabled the firefox extension yesterday because I'm using innerHTML to set the html preview of the markdown - even though I simply do the same as the GitHub page itself. They suggested to use https://github.com/cure53/DOMPurify to sanitize the HTML before setting it to innerHTML.

Would be awesome if someone could provide a PR.

[Akiyamka]

@hediet, I hope it help