Create Stability Pool contract

[chadoh]

This is sometimes called a Liquidity Pool, because that's a familiar blockchain term from decentralized exchanges (DEXes) and automated market makers (AMMs), but we do not actually want to build an AMM here. As Section 2 in the high-level technical overview puts it:

The collateralization and liquidation process within the EquitX platform offers users the ability to collateralize assets and manage risk effectively. Users can secure loans by collateralizing assets, and liquidation occurs as a measure to protect the system's health when the value of collateral changes relative to the debt. The process is meticulously designed to ensure fairness and transparency, with market data provided by Oracles ensuring accurate collateral evaluations.

The idea here is borrowed from Indigo Protocol, built on Cardano. We may be inspired by their smart contract logic. Not that their repo only has one commit, from about a year ago, so is more them showing how their contract worked at a specific moment in time rather than where they actually work. Note also that Cardano uses Haskell!