Greasemonkey 如何在页面中的 *anything* 之前运行？

// ==UserScript==
// @name         Greasemonkey Run Before Anything
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  run Greasemonkey script before anything on the page
// @author       Your Name
// @match        http(s)://*/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    document.addEventListener('DOMContentLoaded', function() {
        // Your code here...
        console.log('Greasemonkey script running before anything on the page');
    }, false);
})();