So, Haider posted on his Facebook timeline, a link to his then newly setup github repo which he had named “rightclick.js.” It was pretty clear what it was about so I gave his code a look. He is using JQuery, and
(for some reason unclear to me,) NodeJS.
I wanted to call it contextmenu.js but there already exists a script by that name, and thus, out of respect, I renamed mine to contextmenus.js. The code happens to be a couple of files that together take up a total of 1812 Bytes of disk space. Everything that you need to know, in order to get it to work for you, is explained in the README.md on the GitHub page.