Support locale with language and region part

docs/config.md

@@ -123,7 +123,9 @@ Remove the `ping/ping` location from the fetched data. This is useful when using
 
 ### `locale`
 
-The language to use for the user interface. Available: `de` (German), `en` (English).
+The locale to use for the user interface, this affects the language and date/time
+formats. Available languages are `de` (German), `en` (English). You can use formats
+like `en-GB`, `en-US`, `de-DE`.
 
 - Type: [`String`]
 - Default: `"en"`

src/i18n.js

@@ -16,7 +16,7 @@ locales.keys().forEach(key => {
 });
 
 export default new VueI18n({
-  locale: config.locale,
+  locale: config.locale.split("-")[0],
   fallbackLocale: "en",
   formatFallbackMessages: true,
   messages,