config property
Maps Breakpoints to SlotLayoutConfigs to determine what Widget to display on which condition of screens.
The SlotLayoutConfigs in this map are nullable since some breakpoints apply to more open ranges and the nullability allows one to override the value at that Breakpoint to be null.
SlotLayout picks the last SlotLayoutConfig whose corresponding Breakpoint.isActive returns true.
If two Breakpoints are active concurrently then the latter one defined in the map takes priority.
Implementation
final Map<Breakpoint, SlotLayoutConfig?> config;