function conjugate(out, a) {
    out[0] = -a[0];
    out[1] = -a[1];
    out[2] = -a[2];
    out[3] = a[3];
    out[4] = -a[4];
    out[5] = -a[5];
    out[6] = -a[6];
    out[7] = a[7];
    return out;
  }
Calculates the conjugate of a dual quat
If the dual quaternion is normalized, this function is faster than quat2.inverse and produces the same result.

@param {quat2} out the receiving quaternion
@param {ReadonlyQuat2} a quat to calculate conjugate of
@returns {quat2} out