* - create constants for thet asset-viewer stack thumbnail sizes
- use 2x selected thumbnail size to set the max-height of the stack-slideshow container.
* - increase the stack-slideshow max-height as it's scrolled
* Revert "- increase the stack-slideshow max-height as it's scrolled"
This reverts commit da4614547acfb8853258071c1b192c8162b86424.
* change asset stack veritcal scroll to horizontal scroll