Shkarko Blockbench 4.12.4

Changes
- Added new Minecraft skin model variants to support the new "Spring to Life" game drop
- Cow: New regular model, warm variant, cold variant
- Pig: New model with support for variants
- Chicken: New cold variant
- Magma cube: New model with updated UV map
- Support for editing subsurface scattering in texture sets
- Auto-load texture sets when opening bedrock model
- When generating multiple MER maps, they are now combined into existing MER textures as an additive layer
- Added a setting to pick combined colors with the color picker. By default, it will now pick the color of the active layer
- Add image edit option to split RGB channels of a texture into separate layers
- Renamed bone binding item slot from "Main Hand" to "Item Slot" to better describe its behavior
Technical changes
- Improved performance of JSON compiler
Fixes
- Fixed # 2731 Error when dragging group into outliner root
- Fixed height map rendering blurry when converted to different pbr channel
- Improved texture set and pbr map name generation
- Fixed #2378 issue with selecting faces in the Face Properties editor
- Fixed PBR actions being available in formats without PBR support
- Fixed context menu not closing when selecting texture from textures panel
- FIxed #2604 "Keep Multi Texture Occupancy" doesn't work for mirrored UV
- Fixed MER map not updating when editing layers
- Fixed issue with loading animation controllers
- Fixed #2723 Multiple images in the same image project can overwrite each other on save
- Fixed issues with generating MER map from existing texture
- Fixed MER map display issues
- Materials can no longer be created from textures that are already in a material
- Fixed #2720 Open Parent & Adopt Textures still does an action when dismissing dialog
- Fixed #2688 NaN is exported to JSON as NaN