Function subscribe

subscribe<T>(eventType, callback): {
    count: number;
    unsubscribe: (() => {
        count: number;
    });
}
Subscribes to a specific event type with a callback function.
Type Parameters
- T = ApiCallback<string>
  The type of the callback function, defaults to ApiCallback.
Parameters
- eventType: string
  The name of the event to subscribe to.
- callback: EventCallback<T>
  The callback function to execute when the event is triggered.
Returns {
    count: number;
    unsubscribe: (() => {
        count: number;
    });
}
An object containing:
- count: The number of active subscriptions for the event type.
- unsubscribe: A function to unsubscribe from the event, which also returns the updated subscription count.
- count: number
- unsubscribe: (() => {
  count: number;
  })
  - - (): {
      count: number;
      }
    - Returns {
      count: number;
      }
      - count: number