slack-night-mode.js

// ==UserScript==
// @name         Slack - Theme
// @version      0.1
// @author       Cezary Daniel Nowak
// @description  try to take over the world!
// @include      *.slack.com/*
// @grant        none
// ==/UserScript==
(function() {
  'use strict';
  
    // INSTALLATION:
    // 1. Select one of CSS files from https://github.com/laCour/slack-night-mode/tree/master/css
    // 2. Paste it below
    // 3. Remove `@-moz-document regexp("https://[^./]*\\.slack\\.com/(?!pricing)(?!security).*") {` part
    //    at the beginning
    // 4. Remove last `}`
    // 5. Save and refresh slack.
  
    const css =
/* ####################################################### */
/* ################### PASTE CSS HERE #################### */`



`/* ######################## END ######################### */
/* ####################################################### */
    
    const style = document.createElement('style');
    style.type = 'text/css';
    style.appendChild(document.createTextNode(css));
    document.head.appendChild(style);
})();