Add basic date & time formatters using navigator language (#404)

Adjacent to #400 — while this isn't yet a proper localization pass, at
least dates & times will now use the user's browser language/locale
settings. When used in Browsertrix, this should ensure dates are
formatted more consistently, at least when the user has a locale with a
language matching one of the supported languages in Browsertrix set in
their browser settings.

Also adds tabular numerals in a few places (e.g. lists of dates/times).

src/url-resources.ts

@@ -8,6 +8,7 @@ import fasSearch from "@fortawesome/fontawesome-free/svgs/solid/search.svg";
 import "keyword-mark-element/lib/keyword-mark.js";
 import { type ItemType } from "./types";
 import { type URLResource } from "./types";
+import { dateTimeFormatter } from "./utils/dateTimeFormatter";
 
 // ===========================================================================
 /**
@@ -544,7 +545,7 @@ class URLResources extends LitElement {
                     </td>
                     <td class="column col-ts is-2">
                       <p class="minihead is-hidden-tablet">Date</p>
-                      ${new Date(result.date).toLocaleString()}
+                      ${dateTimeFormatter.format(new Date(result.date))}
                     </td>
                     <td class="column col-mime is-3">
                       <p class="minihead is-hidden-tablet">Media Type</p>