Add a dimension generic Rotor type

There are already dimension generic Vector types, but there's only a rotation type for 3D: the quaternion.

It's possible to implement general rotors.

3D rotors correspond to quaternions, 2D rotors correspond to complex numbers, and lower dimension rotors don't exist.

This would allow to represent rotations in higher dimensions and to generalize the rotations for writing dimension generic libraries like for physics.

Maybe implementing it requires implementing most of a geometric algebra, so it may be preferred to just implement geometric algebra in a more general way as an extra crate.