app/assets/webpack/application.js
// Polyfills.
import "core-js/fn/array/from";
import "whatwg-fetch";
// Set up rails-ujs.
import Rails from "rails-ujs";
Rails.start();
// Scripts.
import "javascripts/alert";
import "javascripts/nav";
import "javascripts/profile";
// Styles.
import "bootstrap/dist/css/bootstrap";
import "stylesheets/layout";
import "stylesheets/nav";
import "stylesheets/simple_captcha";