Add SeamHttpRequest

[phpnode]

It's often useful to be able to inspect an API Request before it is sent. This PR adds a new class, SeamHttpRequest which implements PromiseLike<T> which holds some information about the request before it is sent to the server. The actual request to the server is made when the SeamHttpRequest is awaited.

e.g.

const request = client.devices.list();
console.log(request.url);
console.log(request.method);
console.log(request.body);
const devices = await request;

Of course the request can be awaited immediately, as normal:

const devices = await client.devices.list();

I'm not married to the naming here so please feel free to bikeshed it 😄

[razor-x]

SeamApiRequest or SeamHttpRequest to match SeamHttp?

[razor-x]

I meant to mention this earlier, but we should add a section to https://github.com/seamapi/javascript-http?tab=readme-ov-file#advanced-usage Name could be "Inspecting the Request"