Add function termsURI

Could make sense to provide a ready-only function for termsURI similar to the read-only hash function for [termsHash](https://github.com/CMTA/CMTAT/blob/master/contracts/modules/wrapper/options/ERC7551Module.sol#L68C14-L68C23) (ERC-7551 deployment version) like you did in your PR


See #315