New docs pages

[sethaxen]

I propose in addition to the dual quaternions docs page introduced in #92 we add 2 more docs pages:

• Representing rotations with unit quaternions
• Extending complex analytic functions to the quaternions

The first would introduce how to use Quaternions directly to transform a point represented as a pure quaternion and also showcase slerp.

The second would give an informal derivation of the method we use for extending complex analytic functions to the quaternions.

[hyrodium]

Representing rotations with unit quaternions

The documentation will be added in #111.