Use data-uk-xxx instead of uk-xxx attributes

Hello maintainers,

Problem/Motivation

With UIkit, we use many attributes as uk-grid or uk-nav...
The framework allows 2 syntax for that : uk-grid or data-uk-grid
The uk-xxx way generate errors with validators as W3C → , while data- attributes are valid in HTML 5.

Moreover, data-uk-xxx way is more legible (less confusion with the framework classes) and the only method supported with React.

Proposed resolution

Replace uk-xxx attributes by data-uk-xxx in preprocess function and templates.

More infos

I planned to make this change in the modules : UIkit components → , Uikit Image Formatter → end UIkit Iconpicker → , which I use in addition of this theme.

Ideally, I wish theme and modules related to UIkit stays aligned, so I would really like to know what you think of this modification ?

Thanks for your answer.