I'd like to know if it is possible to delay the load of any files of a website so we can execute our function for a demanded period of time and load the website files after, doing that with a userscript. Do do so Iwould have to put
// @run-at document-start
in my userscript so that I can call my javascript when the window is open and then I'd like to prevent the window to load any files until I allow it to