* add referenced assembly
* remove unused usings
* MA Merge Blend Tree is VRC specific
because it expects VRC style Animator Layer setup
* PruneParametersPass is VRChat specific
* fix: use FindAvatarTransformInParents() to be more cross platform
* fix MergeArmatureHook: nop logic for PhysBones if we do not dedup PhysBones
* fix AnimatorCombiner: ignore VRC components when non-VRC
btw, is AnimatorCombiner VRC specific?
* conditional compile some VRChat specific tests
* chore: rearrange package structure to have the package at the root
* ci: update CI workflows
* ci: fixing workflow bugs
* ci: recurse building .zip package
* ci: more fixes
* ci: add back in the nadena.dev VPM repo
* ci: fix tests
