Update PRO webpage code, including support for new lines (Tab/Card)

[DascaluDorian]

Hi,

First, thank you for this product, it's great and makes things more easily and accessible :)

So, DASH-Pro user here, I have just migrated the code from the Lite version and found some points that would be great to have an update for.

1. The Pro webpage seems an older version of the Lite one. It does not have the same styling, loading animation, or menu hide option. Is it possible to be updated?

2. Is it possible to support one of the below layouts:

• Custom Tabs with new lines similar to the Statistics tab? I have played a bit with the HTML code, and it's just a div update, that could be easily handled via a Tab attribute.
• Card layout that supports new line? Could be part of the Card Indexing like .setLine(1) or .nextLine(). It would be great to have more flexibility in arranging the layout e.g. 3 Cards on one line, 4 on the next, etc. Indeed, on small screens, this layout will not be kept, but on larger screens, this will remain fixed.

Thanks!