zkSync specific aave-proposals guide

[brotherlymite]

General guide:

• To install zksync foundry on your machine run: curl -L https://raw.githubusercontent.com/matter-labs/foundry-zksync/main/install-foundry-zksync | bash and foundryup-zksync. More info on this repo.
  Please note, this will override your existing forge setup. It is possible to use zksync foundry for non-zksync stuff without much issues, by just not using the --zksync flag
• general build command for zkSync: FOUNDRY_PROFILE=zksync forge test --zksync
• general test command for zkSync: FOUNDRY_PROFILE=zksync forge build --zksync
• zksync/*: should contain all the contracts specific to zksync.

Guide for aave proposals on zkSync:

• generating proposals for zkSync can be done using the generator without any extra specific changes.
• zkSync specific payloads, tests and payload deployment and registering scripts reside in zksync/src/* directory.
• scripts for creating proposal and writeups (.md file), independent if it has zkSync payloads or not reside in the src/* directory and not in zksync/*.
• payloads should be deployed using the generated scripts and the payloadId should be entered manually in the proposal creation script, similar to this.