Can't find i18n in Phoenix docs

How do you make

<html lang="en">

dynamic and not hardcoded in root template using LiveView?

In Laravel it is done like this:

<html lang="{{ str_replace('_', '-', app()->getLocale()) }}">

How do you achieve this in Phoenix?

And again, why isn’t it already there in the first place? Together with the locales and default locale? For example, in Laravel it is set in config/app.php file, namely locale, default_locale, fallback_locale and faker_locale. I mean at least the locale could be put in config/config.exs somewhere by default ;(

As it is now, it seems half baked meaning you got gettext but you are missing locales and local is hardcoded in the root template file.