KubernetesObject type should have a spec field

[bencooper222]

Describe the bug
This type here: https://github.com/kubernetes-client/javascript/blob/6305ecd4308543407910f8db5529f3639bd758c5/src/types.ts#L2C1-L8C1

It should have a spec?: object property on it that is compatible with all derived object's spec type.

** Client Version **
0.18.1

** Server Version **
1.24.1

To Reproduce
N/A

Expected behavior
A spec?: object property added. I've extended it in my own codebase and added the property, I can't see a reason consumers should be expected to do that.

** Example Code**

import type { KubernetesObject } from '@kubernetes/client-node';

export interface CustomKubernetesObject extends KubernetesObject {
  spec?: object;
}

Environment (please complete the following information):

• OS: macOS
• NodeJS Versio: 18
• Cloud runtime: Docker (Debian Bullseye)