Add dual quaternions

[cactusdualcore]

What problem does this solve or what need does it fill?

Dual quaternions can represent rigid body transformations and allow efficient on them.

Describe the solution you'd like

A DualQuat type added to this crate.

Describe alternatives you've considered

Rolling my own from two Quats.

Additional context

Dual quaternions can be very useful when working with physics simulations on rigid bodies.

[bitshifter]

Linking to discussion on this here #698

[fu5ha]

Hey! There is an implementation I did some time ago at Embark here. It was designed and tested as part of a vertex skinning pipeline, so it's not super complete but should be a usable base to start from at least, or potentially be upstresamed in some form:

https://docs.rs/macaw/latest/macaw/struct.DualQuat.html