Thanks, I converted it into a Tampermonkey userscript to use on all the sites.
// ==UserScript==
// @name Underline links
// @namespace http://tampermonkey.net/
// @version 0.1
// @description Underline all the links!
// @author mdaniel
// @match https://*/*
// @match http://*/*
// @grant none
// ==/UserScript==
(() => {
document.querySelectorAll('a[href]').forEach(it => it.style.textDecoration='underline');
})();