How to join multiple rav1e streams into a single output

[dmikushin]

Dear all, as many others do I'm trying to speedup rav1e encoding by deploying multiple threads to encode fragments and join them into a single output video in the end. But I don't understand how exactly should I join multiple contexts each with its own packets into a single joined context. Could you please give a simple instruction what to do to a person who is not fluent in video containers topic. Thank you!