Proposal: Add support for TBTC

because the BTC price went up more than ETH recently, tBTC had a bunch of liquidations that reduced the tBTC supply, and makes it harder for signers to issue more tBTC because their ETH used for collateral to back up the tBTC is worth less than before. this seems like a critical issue for tBTC that will prevent it from scaling well and have enough liquidity to be an useful add for Aave.