Function add

add<T>(a, b, dst?): T
Adds two quaternions; assumes a and b have the same dimension.
Type Parameters
- T extends BaseArgType = number[]
Parameters
- a: BaseArgType
  Operand quaternion.
- b: BaseArgType
  Operand quaternion.
- Optional dst: T
  quaternion to hold result. If not passed in a new one is created.
Returns T
A quaternion that is the sum of a and b.