Research cross-platform codec support [Spike]

This is a little bit vague, but the goal of this task is to find one modern codec for audio and one for video which we can recommend to users. This would have to be something which is either natively supported on the supported platform or which has a third-party code that we can bundle with Qt on the platforms where there is no support.

The idea is that users can convert their assets to these file types, and be guaranteed that playback will be supported on all their target platforms with no surprises.

Note that it is possible that no such formats are found, so this task is only a research/investigation task.