Use Intl.DateTimeFormat instead of moment for date formatting

ts/Intl.d.ts

@@ -0,0 +1,7 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+// https://github.com/microsoft/TypeScript/issues/29129
+declare namespace Intl {
+  function getCanonicalLocales(locales: string | Array<string>): Array<string>;
+}