## Issue Addressed
As specified in the [Beacon Chain API specs](https://github.com/ethereum/beacon-APIs/blob/master/apis/node/syncing.yaml#L32-L35) we should return `is_optimistic` as part of the response to a query for the `eth/v1/node/syncing` endpoint.
## Proposed Changes
Compute the optimistic status of the head and add it to the `SyncingData` response.