From https://meta.stackexchange.com/a/407981/290021
// ==UserScript==
// @name StackExchange dark mode work-in-progress
// @version 2025july4
// @description From https://meta.stackexchange.com/a/407981/290021
// @author daniel.z.tg and Vitaly Zdanevich
// @match https://*.askubuntu.com/*
// @match https://*.mathoverflow.net/*
// @match https://*.serverfault.com/*
// @match https://*.stackapps.com/*
// @match https://*.stackexchange.com/*
// @match https://superuser.com/*
// @run-at document-body
// @namespace https://greasyfork.org/users/22859
// ==/UserScript==
// NOT working for all sites
document.body.classList.add('theme-dark');