Prop 80: [SIPS-076] Proposal to Update stETH Pricing Mechanism

This text proposal is to update the pricing mechanism for stETH in RYETH. The new pricing mechanism is intended to dampen share price volatility. If the proposal is accepted, a steward update will enable the strategist to call the 'cachePriceRouter' function which will effect the change. For more details see the corresponding forum post: https://community.sommelier.finance/t/sips-076-upcoming-proposal-to-update-steth-pricing-mechanism/1184