Errors with popover as alternative

[ztdan4ik]

Hello!
Can be added client option to widget initialization with activefield to use yii validation errors methods for showing an errors during upload instead of bootstrap popover.

Surely, bootstrap is great but it's not standard and many websites decide to not use bootstrap. And as it components for Yii2 I suppose here must be an option an option to not use popover component.

Thank you.