Bug 1924188: Update language selector dropdown

Language selector dropdown should now pre-select the language in a wider range of cases. The selector previously only pre-selected English, Chinese, or Japanese if the browser language was set to en, zh, or ja exactly. The logic should now handle languages we don't support, as well as subsets of languages, such as en-us.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1924188

frontend/public/components/modals/language-preferences-modal.tsx

@@ -1,6 +1,6 @@
 import * as React from 'react';
 import { useTranslation } from 'react-i18next';
-import { TFunction } from 'i18next';
+import i18next, { TFunction } from 'i18next';
 
 import { Dropdown } from '../utils';
 import {
@@ -24,7 +24,8 @@ const LanguagePreferencesModal = (props: LanguagePreferencesModalProps) => {
  }));
  const initLang =
  localStorage.getItem('bridge/language') ||
- langOptions.find((lang) => lang.lang === i18n.language)?.lang;
+ // handles languages we support, languages we don't support, and subsets of languages we support (such as en-us, zh-cn, etc.)
+ i18next.languages.find((lang) => langOptions.some((langOption) => langOption.lang === lang));
  const [language, setLanguage] = React.useState(initLang);
  const { close } = props;
  const submit: React.FormEventHandler<HTMLFormElement> = (e) => {