Renamed $response to $responseClass for better clarity

[mstfblci]

Reflects improved naming for better code readability and maintainability

[mstfblci]

If I use withResponse it conflicts with the $response variable in the hasCustomResponses trait so it is important to replace it with $responseClass.

[mstfblci]

@Sammyjo20 I also changed the name of the trait for better clarity.

[Cbrad24]

This is definitely a breaking change FYI for anyone implementing custom response classes: https://docs.saloon.dev/the-basics/responses

Neither for or against it but as long as it's known it's breaking.

[Sammyjo20]

This is considered a breaking change which I wouldn't be willing to allow until v4 is released.