Add "Preview" button to iOS shortcut's iCloud links, linking to preview.scpl.dev (plus cosmetic changes to the last)

shortcut-preview.user.js

// ==UserScript==
// @name      shortcut-preview
// @namespace https://www.atnbueno.com/
// @match     https://preview.scpl.dev/*
// @match     https://www.icloud.com/shortcuts/*
// @version   1.2
// @grant     none
// ==/UserScript==

(function () {
    "use strict";

    // adds "Preview" button to iCloud shortcut links ("Vista previa" in Spanish)
    if (location.host == "www.icloud.com") {
        let previewLink = document.createElement("a"), previewText;
        if (navigator.language.slice(0, 2) == "es") {
            previewText = "Vista previa"
        } else {
            previewText = "Preview"
        }
        previewLink.appendChild(document.createTextNode(previewText));
        previewLink.href = "https://preview.scpl.dev/?shortcut=" + location.href;
        document.getElementById("shortcut-links").appendChild(previewLink);

    } else if (location.host == "preview.scpl.dev") {
        // changes cosmetic details in the shortcut preview
        var stylesheet = document.createElement("style");
        stylesheet.textContent = `
        header {
            font-family: "SF Pro Text", "Helvetica Neue", Helvetica, Arial, sans-serif;
            margin: 2em;
        }
        header p.versionerror {
            color: darkred;
            margin: 1em auto;
            max-width: 576px;
        }
        header p:not(.versionerror) {
            background: #0169D9;
            border-radius: 8px;
            display: inline-block;
            margin: 1em;
            width: 10em;
            padding: 10px;
        }
        header p:hover {
            opacity: 0.9;
        }
        header a {
            color: white;
            font-size: 110%;
            text-decoration: none;
        }
        header img {
            border-radius: 16px;
            box-shadow: 0 4px 8px 0 rgba(0, 0, 0, .14);
            max-width: 12em;
        }
        div.styles_actionBlockWrapper__3gC_8 {
            max-width: 600px;
        }
        .styles_field__tuaih.styles_multiline__1vzVg {
            height: auto !important;
        }
        `;
        document.documentElement.appendChild(stylesheet);
    }

})();