v2 Documentation for getting Schema in api.Response

[wildan2711]

I've been going through old code, updating it to dgo v2, and I found out that api.Response does not have a Schema field anymore for schema queries.

In the README, it still indicates to get the Schema field from api.Response, while this PR seems to get the schema from the Json field.

Should the documentation be updated?

[mangalaman93]

Thanks for reporting the issue @wildan2711. Raised a PR to fix the documentation.