AV2 request: support alpha transparency

[o-t-w]

For anybody working with video on a web page, there are use cases for transparency. This is sadly not possible with AV1.

https://jakearchibald.com/2024/video-with-transparency/

[Beryesa]

https://aomedia.org/press%20releases/AOMedia-Announces-Year-End-Launch-of-Next-Generation-Video-Codec-AV2-on-10th-Anniversary/ is there any possibility to propose this for consideration before the final av2 release?