Add initial support for UsdShade

[AndrejOrsula]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 337 lines in your changes are missing coverage. Please review.

Project coverage is 17.87%. Comparing base (179fa3a) to head (54c4b9a).

❗ Current head 54c4b9a differs from pull request most recent head 0346acf. Consider uploading reports for the commit 0346acf to get more accurate results

Files	Patch %	Lines
pxr_sys/src/ffi/pxr/sdf/value_type_name.rs	0.00%	325 Missing ⚠️
pxr_sys/src/ffi/pxr/usd_geom/geom_xform.rs	0.00%	6 Missing ⚠️
..._sys/src/ffi/pxr/usd_shade/material_binding_api.rs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
- Coverage   20.55%   17.87%   -2.68%     
==========================================
  Files          34       36       +2     
  Lines        2253     2590     +337     
==========================================
  Hits          463      463              
- Misses       1790     2127     +337     

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