Transparent Shadow Catcher Pass

With the new version 3 Blender has an awesome better shadow catcher. There is just one catch. The pass outputs the shadow on solid white, which effectively hinders its external usage, like the export of product renders with a transparent background, but with a nice shadow, so that they can be used on the web like that. Or for further refinement in Photoshop.

So just outputting the shadow on transparent would fix this.