elGoonishShiveArrowKeys.user.js

// ==UserScript==
// @name        El Goonish Shive Arrow Keys
// @namespace   https://gist.github.com/JulianWebb
// @version     0.1
// @author      Pongles
// @description Adds the ability to navigate the comic using just the left and right arrow keys
// @icon        https://egscomics.com/favicon.ico
// @match       https://egscomics.com/*
// @grant       none
// ==/UserScript==

(function() {
  'use strict';
  
  console.log('Check, Please! Arrow Keys is working!')
  document.onkeydown = function(e) {
    switch (e.key) {
      case 'ArrowLeft':
        let prevPage = document.querySelector(".cc-prev");
        prevPage.click()
        break;
      case 'ArrowRight': 
        let nextPage = document.querySelector(".cc-next");
        nextPage.click();
        break;
      default: return;
    }
  }
})();