Add CSS class to <html>

I implemented different themes using the

tw-colors

tw-colors

tailwind package. Now I have to render the configured class name from .env into the <html> tag, e.g.

<html class="classic-theme">

<html class="classic-theme">

.
But I could not find any way to achieve this so far. I created

resources/views/layouts/app.blade.php

resources/views/layouts/app.blade.php

but this file seems to be ignored for the admin panel.

Edit: Or alternatively I can add

<html data-theme='classic'>
      ...
</html>

<html data-theme='classic'>
      ...
</html>