Use iPad Camera while multitasking

When using other Mac and Windows devices I can use other apps and still have Discord call participants see my camera feed. Implementing these changes to the iOS and iPadOS apps would greatly improve the video calling experience.

https://developer.apple.com/documentation/avkit/accessing_the_camera_while_multitasking_on_ipad#4017605

https://developer.apple.com/documentation/avkit/adopting_picture_in_picture_for_video_calls