Enable xSUSHI on FUSE

Summary

This is a proposal to add xSUSHI as a collateral option for borrowing and lending on FUSE Pool 3.

What is xSUSHI?

xSUSHI is the staked, yield-earning form of $SUSHI, the native token of the SushiSwap protocol. xSUSHI earns a portion of fees from SushiSwap usage, primarily its AMM. Its APY varies with an average around 15%. For more info, see https://app.sushi.com/sushibar

Why add xSUSHI on FUSE?

Currently, FUSE supports vanilla $SUSHI but not xSUSHI. Unstaked SUSHI is not yield-generating, so this is a disadvantage versus other lending platforms like Aave and CREAM which support xSUSHI deposits.

Is this technically viable?

Jack has confirmed that Rari has the code to support xSUSHI