Add official way to opt out of using Get

# Background

- https://github.com/CreateAPI/CreateAPI/pull/82#discussion_r936948277

As it stands, to opt out of using Get, you must do three things:

1. Use `--module` mode
2. Update `paths.imports` to be an empty array
3. Provide your own `Request` shim

While we believe that using CreateAPI with Get it the quickest and easiest option, we understand that not everybody is in a position to adopt Get. As a result, we need to provide a better way to disable use of the dependency.

# Description

I can think of three scenarios:

1. You want to use Get and you are happy with the default behaviour
2. Your networking client already defines it's own `Request` in a module that should be imported
3. You will build your networking client on top of the generated code and want a `Request` type generated for you

I did at first think that we should just generate `Request` if you opted not to use Get, but this will put some people who already import a different module defining `Request` in a situation where they can't use the generated code. It might be that like Get, the `Request` type is used for manually crafted requests too so defining it inside the CreateAPI generated package might not be appropriate.

Not sure how best to handle this...