Add support for Rari Capital tokens

Summary: Add support for Rari Capital tokens as borrowing collateral

Rari Capital, a robo-advisor protocol that takes deposited assets and reallocates them into the highest yield opportunities (already has Compound integrated) just launched v2 of their product.

With three pools, stable, yield, and ETH, each catering to a different risk portfolio or asset exposure, they have several ecosystem tokens, similar to cDai (represents 1 stablecoin deposited + interest). We have also launched their governance token, $RGT, and its public liquidity mining program. With how accessible $RGT earning is (just have to deposit into the platform), Compound should add all four tokens (3 pool tokens and RGT) as collateral for borrowing. This would allow Rari depositors to then borrow against their Rari tokens and increase borrowing demand, increasing interest rates, and volume.

This is an early-stage idea, and I don’t have a formal proposal yet, however, I believe this to be a good first step.

Useful links:
Rari docs: