Authorizers: example contract snippet is missing import and V0

[dcroote]

Relevant section. I needed:

//SPDX-License-Identifier: MIT
pragma solidity 0.8.9;

import "@api3/airnode-protocol/contracts/authorizers/interfaces/IAuthorizerV0.sol";

And needed to use IAuthorizerV0 instead of IAuthorizer i.e.

contract everythingAuthorized is IAuthorizerV0

[dcroote]

@martinkolenic - moving to Done as this is already being tested in CI as part of api3dao/airnode#1488. See here:

https://github.com/api3dao/airnode/blob/f2ca933df6bd99d840618ff8a2e884141a2af1a0/packages/airnode-examples/contracts/coingecko-e2e/EverythingAuthorizer.sol