Limit the waiting queue to 2 toasts

**Do you want to request a *feature* or report a *bug*?**
feature

**What is the current behavior?**
When using `limit`, all pending toasts will be queued. Coming after a while, toasts will start playing from the most recent to the oldest one.

**What is the expected behavior?**
We would like to keep a `limit=1` with a `queueMax=2` (property not existing at the moment), so that we aren't spammed by toasts when coming back to the page after a while, especially since old toasts have become irrelevant by now.
We want to keep the 2 most recent notifications in the queue, thus the newest toast should remove the second oldest toast from the queue.

Would it be possible to add this new property to a container ? Or maybe add another param to `ClearWaitingQueueParams` when calling `toast.clearWaitingQueue` ?

Thank you for considering this feature.