VOXEDIT: ik solver for editing the transforms

[mgerhardy]

implement an armature (is a hierarchical collection of bones) class for this that performs the ik solving.

#256 might be related

The VXRFormat.cpp contains a few ik parameters for sandbox voxel format. Implementing those might be useful for testing and validating the ik solver. See #182

https://github.com/V-Sekai/many_bone_ik

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this will also help to improve on importing animations from e.g. gltf where the
animation is done in bones and not via transforms of the meshes

[mgerhardy]

• https://iquilezles.org/articles/simpleik/
• https://github.com/guillaumeblanc/ozz-animation
• https://github.com/Nor-s/Anim