Fix support for texture transform for anisotropy map

[zeux]

This is necessary to make glTF files that use KHR_materials_anisotropy together with KHR_texture_transform work properly.

Tested using gltfpack and updated model from glTF-Sample-Models that specifies the texture properly + some local fixes to the model:

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
642.7 kB (159.1 kB)	642.8 kB (159.1 kB)	+147 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

Filesize dev	Filesize PR	Diff
432.5 kB (104.8 kB)	432.7 kB (104.8 kB)	+146 B

[WestLangley]

Note: the model is currently under development.

See KhronosGroup/glTF-Sample-Models#366

[mrdoob]

/ping @elalish

[elalish]

LGTM, thanks!