Function encode_chain_head_event 

pub fn encode_chain_head_event(
    request_id: &str,
    event: &ChainHeadEvent,
) -> Vec<u8> 

Encode a chainHead_v1_followEvent receive message (tag 79).

Wire format: request_id + 0x4F (79) + 0x00 (v1) + ChainHeadEvent_SCALE