enables looping when you've opened a video file
// ==UserScript==
// @name loop video files
// @namespace hvideolooper
// @author h
// @description enables looping when you've opened a video file
// @include *.webm
// @include *.mp4
// @run-at document-start
// @version 0
// @grant none
// ==/UserScript==
document.getElementsByTagName("video")[0].setAttribute("loop", "true");