Tasks queuing

[janusn]

Please add tasks queuing.

[jhj0517]

Hi. I believe it might be related to concurrency_limit here:

• https://www.gradio.app/guides/queuing#configuring-the-queue

Currently concurrency_limit is not set and is used as 1 by default.
Probably adding concurrency_limit as a CLI option for app.py and letting users customize it is the way to go.

[jhj0517]

Increasing the concurrency_limit did not work as expected on my test.
Any PR or suggestions on this would be appreciated.

[jhj0517]

I just figured out that btn.click(trigger_mode="multiple",) does the thing.
But it seems there's a little more to do, so I'd mark this as WIP.