fix: Morphtarget Meshes Can Also Include GarmentSupport

[effs]

Implemented

• .morphtargets can include GarmentSupport data, i.e. they can (typically) shrink under clothing when GS is active
• GarmentSupport is checked by default for import for both .mesh and .morphtarget (it was already default on export)

NB: GarmentSupport must be first shapekey/target and let's require that naming too.

Usage

General GarmentSupport guide on the redmodding wiki

1. In Blender, create a shapekey named GarmentSupport for each submesh that you want to deform for GS, typically shrinking the mesh a bit so that it doesn't clip with tighter fits
2. Ensure GarmentSupport is the first shapekey (after Basis)
3. Include _GARMENTSUPPORTWEIGHT and _GARMENTSUPPORTCAP attributes
4. Blender-Export w/ the cp77 Blender plugin
5. Import into wkit with the garment support option checked (should be by default), first the .mesh, then the .morphtarget just like usual

Detes

Both morphtarget and GS data are encoded in glTF targets so we need to be careful which targets we use for which purposes.

Issues/TODO

The following tickets still have relevant open questions or fixup/cleanup, but this is probably safe enough to test as is.

• Mesh Import Bounds Calculated Without GarmentSupport #1504
• Remove Empty Mesh Support Via Nodes on Import Unless Need Validated #1505
• Mesh Import Needs to Actually Check it's Working with GarmentSupport Targets #1506