feat: add a method for getting raw responses

[scriptnull]

I would like a bit more control at some place. Having this will help with that.

[imperfect-fourth]

@scriptnull trying to understand the need here. Can you give an example use case of why/where you would need the raw http response object?

[scriptnull]

sure. There is a place where I am doing Do() to perform a gql request and it is returning error response with http status code: %d error. I can see the HTTP status code with that error, but there is more useful information in the response body about the error which I would like to access. Having Raw() would give me a way to access that information.

[scriptnull]

I belive Do can also use Raw as it is superset of that functionality. Would you like me to do that as part of this PR?

[imperfect-fourth]

cool! let's make Do use Raw