All `css()` methods, regardless of the instance they belong to, return a CSSClass instance, which has useful methods and properties to deal with the className generated and inserted into elements.
CSSClass
Currently it only has one method and one property, but maybe in the future we can add new features.
CSSClass.name
The name of the css class.
CSSClass.remove()
Removes the class from all elements that contain it.
