Hi. I'd like to add a back to top button like the one from this wiki: https://www.sorumu.com/S%C3%B6zl%C3%BCk:Anasayfa
I've seen they've used the exact same example from here: https://www.w3schools.com/howto/howto_js_scroll_to_top.asp
I added what needed to be added to common.css and common.js, but I am not exactly sure where and how to add the HTML element. I have read this article and then added the HTML element inside common.js, as seen here under 'back to top': http://dragon-mania-legends-wiki.mobga.me/MediaWiki:Common.js
Would anyone please shed a little bit of light as to where I am going wrong?