New CSS component: State

[devmount]

Is your feature request related to a problem? Please describe.
Sometimes an area should indicate a certain state for the user to know, something is possible which isn't there at the moment.

Describe the component you'd like for that problem

• Introducing a new class .state-muted e.g. for an empty section which awaits user input to show something
• Introducing a new class .state-higlighted e.g. for an accentuated section which awaits a user action like drag and drop.