Errors in docs for Bootstrap 4 controls  #154

I discovered some errors in documentation for Bootstrap 4 controls.

ListGroup

https://www.dotvvm.com/docs/2.0/controls/bootstrap4/ListGroup

Sample 5: Badges
There is typo "USe".

Popover

https://www.dotvvm.com/docs/4.0/controls/bootstrap4/Popover

Sample 6: Popover Template
The image inside the popover is missing.

Badge

https://www.dotvvm.com/docs/4.0/controls/bootstrap4/Badge

Sample 3: Badge as Link or Button
Sample does not show anything.

Breadcrumb:

https://www.dotvvm.com/docs/4.0/controls/bootstrap4/Breadcrumb

Sample 1: Static Breadcrumbs
Sample does not show anything.

Sample 2: Selected Items
Sample does not show anything.