Support block_gossip topic in Beacon API /eth/v1/events

[samcm]

Describe the bug
Related discussion on Beacon API repo: ethereum/beacon-APIs#349

To Reproduce
Steps to reproduce the behavior:

• Subscribe to event stream with block_gossip
• {"code":400,"message":"Invalid topics value","stacktraces":["Incorrect event's topic value"]}

Screenshots
N/A

Additional context
N/A

[tersec]

Not part of spec.

[samcm]

https://github.com/ethereum/beacon-APIs/blob/ee736456c7639fe952c5742834033e6ef700b12b/apis/eventstream/index.yaml#L60

Does it need to be defined somewhere else?

[tersec]

Ah, misunderstood the spec PR. It's there, it's just not exactly semantically defined. Ok.