[Feature] Control center visibility class

[System64fumo]

Is your feature request related to a problem? Please describe.
It would be nice to have a visible/hidden class for when the notification center is open or visible.

Describe the solution you'd like
Addition of a visible/hidden class when opening/closing the notification center.
Addition of a visible/hidden class when a notification shows up (Outside the notification center).

Additional context
I want to add animations, So far i've added a slide in animation for notifications (Slide from top of screen to position)
But i also want to do this for the notification center, It is possible it it would only play once since there's no way (as far as i'm aware) to detect if the notification center is open or closed.