add SupervisorSyncStatus return object to specs

[nonsense]

Description

This PR is adding a description of the SupervisorSyncStatus return object, as it is being updated at ethereum-optimism/optimism#15624

---

The linked PR is adding two new fields to the SupervisorChainSyncStatus struct:

type SupervisorChainSyncStatus struct {
...
	LocalSafe   BlockID  `json:"localSafe"`
	CrossUnsafe BlockID  `json:"crossUnsafe"`
...
}

[nonsense]

I will mark this as ready for review as soon as the linked PR is merged, as it is changing one of the structs defined here.

[dhyaniarun1993]

I will mark this as ready for review as soon as the linked PR is merged, as it is changing one of the structs defined here.

I believe the spec PR should be merged first since it defines the structure that the implementation PR is based on. The implementation PR is meant to follow the spec, not the other way around.

[clabby]

I will mark this as ready for review as soon as the linked PR is merged, as it is changing one of the structs defined here.

I believe the spec PR should be merged first since it defines the structure that the implementation PR is based on. The implementation PR is meant to follow the spec, not the other way around.

+1. If you take this out of draft, we can merge it now.