Add close X button on kendo.ui.Validator alerts (.k-invalid-msg)

[jlchereau]

I would have made a suggestion on uservoice but I am out of votes and cannot contribute anymore.

Responsive design makes space tight for displaying validator alerts, which in this case become annoying. The exemple below covers other fields.

It would be nice to be able to close them like notifications (see close X in the exemple below).