Proposal: Add mode agnostic css class

[alan-agius4]

We'd like to propose a bit of a change in the components base class. I kinda did a bit of a concept. And i am willing to go through all the components and implement this.

alan-agius4@5b3b5a2

basically at the moment for a component a class is added according to the mode set ex: .item-md, .item-wp, .item-md. However, if you'd like to override or add some for all modes it would be quite useful to have a mode agnostic class that you can target ex .item.

To be discussed with @adamdbradley and @brandyscarney.

[zakton5]

Agreed, I've had to adjust many styles because of mode-specific classes. As of now, it just causes us to make more CSS

[zakton5]

Related, most likely duplicate: #8533