Incorrect calculation of normalisation

[jwpleow]

https://github.com/neka-nat/dq3d/blob/365c363a47e3ec60fce0bf7b260f1e59d3556b24/dq3d/DualQuaternion.h#L244

Hi, I think you have miscalculated the normalisation of the dual quaternion - you've already normalised both the primary and dual parts by the primary part's norm, so following the equation in https://math.stackexchange.com/questions/4445771/normalizing-a-dual-quaternion, you should only need to subtract the dual part by the dot product multipled by m_real, without needing the * lengthSqr?