Describe the bug

When Converse is used in embedded mode, the viewport size gives no information about the available size for Converse.

These lines:

    if (view_mode === 'overlayed') {
        chat_area_classes = 'd-none d-md-flex col-s-10 col-md-8';
        sidebar_classes = 'col-xs-12 col-s-2 col-md-4';
    } else {
        chat_area_classes = 'd-none d-md-flex col-md-8 col-xl-10';
        sidebar_classes = 'col-xs-12 col-md-4 col-xl-2';
    }

These lines relies on the viewport size to change the width of the muc sidebar (and sometime hide the chat area).

But as said, in embedded view mode, the viewport gives little information on the chat width.
You can for example have a 1480*1024 viewport, but only 400*800 for the embedded chat.

Expected behavior

These classes should not be used in embedded mode.
Flex should automatically resize chat area and muc sidebar.