add support for a timeout

[Zhell1]

If you reach the throttle threshold, especially in the case of a large interval, it becomes necessary to timeout requests so that you can handle them otherwise. In my case I needed to throttle based on a number of requests per day, and when that level is reached I want to timeout requests & empty the queue so that I can handle them using another API.

This PR solves this issue by adding a new parameter to provide a timeout for requests after which they are removed from the queue and the promise rejects with an error.