gridview glyphicon

In my Gridview, I have a column called "IMPORTANT" - and I would like to display a star glyphicon (glyphicon glyphicon-star) in the cell when the value for important is set to 1.

How do I do that?

Many thanks

http://www.yiiframework.com/doc-2.0/yii-grid-datacolumn.html#$value-detail