eth2 quick update no. 13

Testnets, testnets, testnets! tl;dr Medalla multi-client testnet launch date set 🚀 Initial beta attacknets are up. Calling all whitehats 👩‍🍳 Exciting progress on the eth1+eth2 merger 👊 Medalla testnet Following the excellent stability of Altona and based on conversations with eth2 client teams, Medalla - the next multi-client testnet -......