Inform user about rank in queue

[rgaudin]

On the status page indicating that the task is pending, we already indicate whether the task has started or not.
When it hasn't, we should indicate the position in the queue as there is no possibility for a user to know if the task will be picked up in a reasonable amount of time or not.

As we don't use a queue but zimfarm fetches tasks as it pleases, we can only provide an approximation.
Knowing that we have a single worker processing two tasks as once, we can sort the requests by creation time and infer some fake rank in a fake queue.

This should be good enough for now.

[Darkcoder011]

means we just want to show our customer that the Work is Processing but the Work is Actually is in pending just like WINRAR

@rgaudin

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.