Set default div class for element group div

[joostdebruijn]

Is your feature request related to a problem? Please describe.
I would like to make a horizontal Bootstrap form layout like here: https://getbootstrap.com/docs/5.1/forms/layout/#horizontal-form

Describe the solution you'd like
It should be possible to add a class in this specific div via the default_classes config, however it looks like this is not possible at this moment:

aire/views/group.blade.php

Line 6 in 46bc69a

<div class="{{ $prepend || $append ? 'flex' : '' }}">

Describe alternatives you've considered
None.

Additional context
Maybe I will prepare a pull request for this at a later moment.