is
Returns the current visibility state as a boolean, observing any reactive sources (such as VisibilityState.ScrollAware.scrollState) as needed.
This composable function evaluates the VisibilityState and returns true if the element should be visible, false otherwise. For VisibilityState.ScrollAware, it observes the scroll position and compares it against the threshold.
Return
true if the element should be visible based on the current state, false otherwise.