Add contribution and proof event (#2527)

## Issue Addressed

N/A

## Proposed Changes

Add the new ContributionAndProof event: https://github.com/ethereum/beacon-APIs/pull/158

## Additional Info

N/A

Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/http_api/src/lib.rs

@@ -2472,6 +2472,9 @@ pub fn serve<T: BeaconChainTypes>(
                                 api_types::EventTopic::ChainReorg => {
                                     event_handler.subscribe_reorgs()
                                 }
+                                api_types::EventTopic::ContributionAndProof => {
+                                    event_handler.subscribe_contributions()
+                                }
                             };
 
                             receivers.push(BroadcastStream::new(receiver).map(|msg| {