vol*: overlays of volumes and segmentations

[alisterburt]

This is a high value feature for volume rendering identified in #1086 and is already available in mol*

my favourite mol* example: https://molstar.org/viewer/?snapshot-url=https%3A%2F%2Fmolstarvolseg.ncbr.muni.cz%2Fsnapshots%2Femd-1014.molj&snapshot-url-type=molj&prefer-webgl1=1

The only reason I add this issue is because I don't see an example showing how segmentations look on top of volumes rendered with the direct volume representation. If this doesn't already work well then that is what we should add to mol*

[arose]

You renderer a direct-volume and segmentations as isosurface together, but I think there are many UI/UX improvements possible.

mol-star_state_2024-4-28-13-46-48.zip rename extension to .molx

[alisterburt]

Love it! Thanks for the example @arose - I'll play around :)