[BIP-28] Approve bETH design and deployment

Summary This proposal aims to agree the implementation of bETH, a basket of liquid staked ETH tokens.

Background Bao needs an interest-bearing Ethereum token to use as collateral for baoUSD, and in future baoETH. A basket of liquid-staked ETH derivatives (LSDs) would encourage the adoption of a healthy balance of liquid-staking providers whilst minimizing risk to the solvency of our synthetics simultaneously. It can also be a good product on its own, allowing other communities to adopt it instead of a single LSD.

Goals Create the best interest-bearing Ethereum collateral possible. Provide an easy way for the crypto community to diversify between liquid staking providers

Detailed solution is explained here : https://gov.bao.finance/t/bip-28-approve-beth-design-and-deployment/1211