[Feature]: Jacobian: Support for a given point on a link body

[Tadinu]

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What feature or enhancement are you proposing?

Currently, RigidEntity.get_jacobian considers an existing link as input, it would be great to have it generalized as accepting a point on a link body. See discussion https://github.com/Genesis-Embodied-AI/Genesis/discussions/873 for reference.

Motivation

Jacobian in MuJoCo supports calculation on how a "spatial frame anchored at the given point will translate and rotate if we make a small change to the kinematic configuration". Namely, mj_jac describes "the local linear relationship between the degrees-of-freedom and a given point".

Potential Benefit

Example usecase: To be used in collision constraint formulation for an LSQP controller, like in mink