refactor: added HTTPURLResponse to returned result tuple

[lukepistrol]

Before

let result = await pexels.getCuratedPhotos()

switch result {
case .failure(let error):
    print(error.description)
case .success(let (data, paging)):
    // access photos
    // data -> [PSPhoto]
    // paging -> PSPagingInfo
}

After

let result = await pexels.getCuratedPhotos()

switch result {
case .failure(let error):
    print(error.description)
case .success(let (data, paging, response)):
    // access photos
    // data -> [PSPhoto]
    // paging -> PSPagingInfo
    // response -> HTTPURLResponse
}