fix(lang): respect fallback languages

If `navigator.languages` returns `['da', 'en-US', 'en']`, and the Danish
language is not available, the user interface should be in English.

Currently it is shown in Norwegian, because only `'da'` is taken into
account when deciding on the preferred language (and `match` selects
`nb-NO` using the default `'best fit'` algorithm).

While the Norwegian and Danish languages are similar, I would argue that
this is a bug, as `navigator.languages` cleary states that the fallback
language should be English.

Another potential solution would be to pass `{ algorithm: 'lookup' }` to
the `match` function. However, this might break some cases when a
`'best fit'` approach would be appropriate (e.g. Swiss German falling
back to German).

See https://helvede.net/@jwcph/113497955274343365.

src/utils/lang.js

@@ -1,9 +1,9 @@
 import { i18n } from '@lingui/core';
 import {
-  detect,
   fromNavigator,
   fromStorage,
   fromUrl,
+  multipleDetect,
 } from '@lingui/detect-locale';
 import Locale from 'intl-locale-textinfo-polyfill';
 
@@ -54,7 +54,7 @@ export async function activateLang(lang) {
 }
 
 export function initActivateLang() {
-  const lang = detect(
+  const languages = multipleDetect(
     fromUrl('lang'),
     fromStorage('lang'),
     fromNavigator(),
@@ -62,7 +62,8 @@ export function initActivateLang() {
     DEFAULT_LANG,
   );
   const matchedLang =
-    ALL_LOCALES.find((l) => l === lang) || localeMatch(lang, ALL_LOCALES);
+    languages.find((l) => ALL_LOCALES.includes(l)) ||
+    localeMatch(languages, ALL_LOCALES);
   activateLang(matchedLang);
 
   // const yes = confirm(t`Reload to apply language setting?`);