add guardian information

docs/contributing/governance/proposal-process.md

@@ -58,3 +58,10 @@ The default template for proposals can be found on [Github](https://github.com/y
 ## Implementation
 
 Once a Snapshot votes have passed, changes will be implemented by Yearn's protocol or operations team and signed by the multi-sig, if necessary.
+
+## Guardian Role
+
+Per [YIP-81](https://snapshot.box/#/s:veyfi.eth/proposal/0x6f3082db2cef3e0c254e569580d063cb14130a92d0bf1729bef342a386e419f2), the [Yearn Multisig](/developers/security/multisig) (AKA yChad) will serve in the Guardian role to steward and protect the Yearn Protocol and its participants.
+
+- The Guardian role is defined as being able to "nullify a proposal or governance decision but cannot make proposals".
+- The Guardian role can be re-assigned via a YIP vote.

docs/developers/security/multisig.md

@@ -6,6 +6,10 @@ The multisig is implemented by a 6-of-9 multi-signature wallet. The members of t
 
 The multisig is implemented as a Gnosis Safe. The multisig's assets, transactions, and signers can be viewed using [Gnosis's Web UI](https://app.safe.global/home?safe=eth:0xFEB4acf3df3cDEA7399794D0869ef76A6EfAff52). If there is a need to trustlessly audit Yearn's multisig (without trusting the Gnosis site), the Gnosis Safe web app source code can be found on Github [here](https://github.com/safe-global/safe-wallet-web).
 
+## Protocol Guardian Role
+
+Per [YIP-81](https://snapshot.box/#/s:veyfi.eth/proposal/0x6f3082db2cef3e0c254e569580d063cb14130a92d0bf1729bef342a386e419f2), the Yearn Multisig (AKA yChad) will serve in the Guardian role to steward and protect the Yearn Protocol and its participants. The Guardian role is defined as being able to "nullify a proposal or governance decision but cannot make proposals". The Guardian role can be re-assigned via a YIP vote.
+
 ## Members
 
 Multisig membership can be validated from the Gnosis UI [here](https://app.safe.global/settings/setup?safe=eth:0xFEB4acf3df3cDEA7399794D0869ef76A6EfAff52).