experiments.user.js

// ==UserScript==
// @name         Experiments
// @namespace    Violentmonkey Scripts
// @version      0.1
// @description  Experiements
// @author       adryd
// @match        https://discord.com/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=discord.com
// @grant        none
// @run-at       document-start
// ==/UserScript==

(function() {
    'use strict';
    function globalEnvPatcher() {
        let GLOBAL_ENV;
        Object.defineProperty(window, "GLOBAL_ENV", {
            set: function set(value) {
                GLOBAL_ENV = value
                window.GLOBAL_ENV.RELEASE_CHANNEL = "staging"
            },
            get: function get() {
                return GLOBAL_ENV
            },
            configurable: true
        })
    }
    const script = document.createElement("script")
    script.text = "(" + globalEnvPatcher.toString()+")()"
    document.documentElement.appendChild(script);
})();

What does this userscript do?